diff --git a/doc/rdoc/markup_reference.rb b/doc/rdoc/markup_reference.rb
index c59f12cfe3..b3d1d97f4f 100644
--- a/doc/rdoc/markup_reference.rb
+++ b/doc/rdoc/markup_reference.rb
@@ -51,23 +51,37 @@ require 'rdoc'
#
# === Blocks
#
-# It's convenient to think of markup input as a sequence of _blocks_,
-# such as:
+# It's convenient to think of \RDoc markup input as a sequence of _blocks_
+# of various types (details at the links):
#
-# - {Paragraphs}[rdoc-ref:RDoc::MarkupReference@Paragraphs].
-# - {Verbatim text blocks}[rdoc-ref:RDoc::MarkupReference@Verbatim+Text+Blocks].
-# - {Code blocks}[rdoc-ref:RDoc::MarkupReference@Code+Blocks].
-# - {Block quotes}[rdoc-ref:RDoc::MarkupReference@Block+Quotes].
-# - {Bullet lists}[rdoc-ref:RDoc::MarkupReference@Bullet+Lists].
-# - {Numbered lists}[rdoc-ref:RDoc::MarkupReference@Numbered+Lists].
-# - {Lettered lists}[rdoc-ref:RDoc::MarkupReference@Lettered+Lists].
-# - {Labeled lists}[rdoc-ref:RDoc::MarkupReference@Labeled+Lists].
-# - {Headings}[rdoc-ref:RDoc::MarkupReference@Headings].
-# - {Horizontal rules}[rdoc-ref:RDoc::MarkupReference@Horizontal+Rules].
-# - {Directives}[rdoc-ref:RDoc::MarkupReference@Directives].
+# - {Paragraph}[rdoc-ref:RDoc::MarkupReference@Paragraphs]:
+# an ordinary paragraph.
+# - {Verbatim text block}[rdoc-ref:RDoc::MarkupReference@Verbatim+Text+Blocks]:
+# a block of text to be rendered literally.
+# - {Code block}[rdoc-ref:RDoc::MarkupReference@Code+Blocks]:
+# a verbatim text block containing Ruby code,
+# to be rendered with code highlighting.
+# - {Block quote}[rdoc-ref:RDoc::MarkupReference@Block+Quotes]:
+# a longish quoted passage, to be rendered with indentation
+# instead of quote marks.
+# - {List}[rdoc-ref:RDoc::MarkupReference@Lists]: items for
+# a bullet list, numbered list, lettered list, or labeled list.
+# - {Heading}[rdoc-ref:RDoc::MarkupReference@Headings]:
+# a section heading.
+# - {Horizontal rule}[rdoc-ref:RDoc::MarkupReference@Horizontal+Rules]:
+# a line across the rendered page.
+# - {Directive}[rdoc-ref:RDoc::MarkupReference@Directives]:
+# various special directions for the rendering.
+# - {Text Markup}[rdoc-ref:RDoc:MarkupReference@Text+Markup]:
+# text to be rendered in italic, bold, or monofont.
#
-# All of these except paragraph blocks are distinguished by indentation,
-# or by unusual initial or embedded characters.
+# About the blocks:
+#
+# - Except for a paragraph, a block is distinguished by its indentation,
+# or by unusual initial or embedded characters.
+# - Any block may appear independently
+# (that is, not nested in another block);
+# some blocks may be nested, as detailed below.
#
# ==== Paragraphs
#
@@ -98,12 +112,13 @@ require 'rdoc'
#
# A paragraph may contain nested blocks, including:
#
-# - Verbatim text blocks.
-# - Code blocks.
-# - Block quotes.
-# - Lists of any type.
-# - Headings.
-# - Horizontal rules.
+# - {Verbatim text blocks}[rdoc-ref:RDoc::MarkupReference@Verbatim+Text+Blocks].
+# - {Code blocks}[rdoc-ref:RDoc::MarkupReference@Code+Blocks].
+# - {Block quotes}[rdoc-ref:RDoc::MarkupReference@Block+Quotes].
+# - {Lists}[rdoc-ref:RDoc::MarkupReference@Lists].
+# - {Headings}[rdoc-ref:RDoc::MarkupReference@Headings].
+# - {Horizontal rules}[rdoc-ref:RDoc::MarkupReference@Horizontal+Rules].
+# - {Text Markup}[rdoc-ref:RDoc:MarkupReference@Text+Markup].
#
# ==== Verbatim Text Blocks
#
@@ -140,6 +155,9 @@ require 'rdoc'
#
# This is not verbatim text.
#
+# A verbatim text block may not contain nested blocks of any kind
+# -- it's verbatim.
+#
# ==== Code Blocks
#
# A special case of verbatim text is the code block,
@@ -173,6 +191,9 @@ require 'rdoc'
# Pro tip: If your indented Ruby code does not get highlighted,
# it may contain a syntax error.
#
+# A code block may not contain nested blocks of any kind
+# -- it's verbatim.
+#
# ==== Block Quotes
#
# You can use the characters >>> (unindented),
@@ -181,6 +202,7 @@ require 'rdoc'
#
# Example input:
#
+# Here's a block quote:
# >>>
# Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer
# commodo quam iaculis massa posuere, dictum fringilla justo pulvinar.
@@ -194,27 +216,30 @@ require 'rdoc'
# Rendered HTML:
#
# >>>
-# Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer
-# commodo quam iaculis massa posuere, dictum fringilla justo pulvinar.
-# Quisque turpis erat, pharetra eu dui at, sollicitudin accumsan nulla.
+# Here's a block quote:
+# >>>
+# Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer
+# commodo quam iaculis massa posuere, dictum fringilla justo pulvinar.
+# Quisque turpis erat, pharetra eu dui at, sollicitudin accumsan nulla.
#
-# Aenean congue ligula eu ligula molestie, eu pellentesque purus
-# faucibus. In id leo non ligula condimentum lobortis. Duis vestibulum,
-# diam in pellentesque aliquet, mi tellus placerat sapien, id euismod
-# purus magna ut tortor.
+# Aenean congue ligula eu ligula molestie, eu pellentesque purus
+# faucibus. In id leo non ligula condimentum lobortis. Duis vestibulum,
+# diam in pellentesque aliquet, mi tellus placerat sapien, id euismod
+# purus magna ut tortor.
+#
+# Note that, unlike verbatim text, single newlines are not honored,
+# but that a double newline begins a new paragraph in the block quote.
#
# A block quote may contain nested blocks, including:
#
# - Other block quotes.
-# - Paragraphs.
-# - Verbatim text blocks.
-# - Code blocks.
-# - Lists of any type.
-# - Headings.
-# - Horizontal rules.
-#
-# Note that, unlike verbatim text, single newlines are not honored,
-# but that a double newline begins a new paragraph in the block quote.
+# - {Paragraphs}[rdoc-ref:RDoc::MarkupReference@Paragraphs].
+# - {Verbatim text blocks}[rdoc-ref:RDoc::MarkupReference@Verbatim+Text+Blocks].
+# - {Code blocks}[rdoc-ref:RDoc::MarkupReference@Code+Blocks].
+# - {Lists}[rdoc-ref:RDoc::MarkupReference@Lists].
+# - {Headings}[rdoc-ref:RDoc::MarkupReference@Headings].
+# - {Horizontal rules}[rdoc-ref:RDoc::MarkupReference@Horizontal+Rules].
+# - {Text Markup}[rdoc-ref:RDoc:MarkupReference@Text+Markup].
#
# ==== Lists
#
@@ -240,12 +265,13 @@ require 'rdoc'
# A list item may contain nested blocks, including:
#
# - Other lists of any type.
-# - Paragraphs.
-# - Verbatim text blocks.
-# - Code blocks.
-# - Block quotes.
-# - Headings.
-# - Horizontal rules.
+# - {Paragraphs}[rdoc-ref:RDoc::MarkupReference@Paragraphs].
+# - {Verbatim text blocks}[rdoc-ref:RDoc::MarkupReference@Verbatim+Text+Blocks].
+# - {Code blocks}[rdoc-ref:RDoc::MarkupReference@Code+Blocks].
+# - {Block quotes}[rdoc-ref:RDoc::MarkupReference@Block+Quotes].
+# - {Headings}[rdoc-ref:RDoc::MarkupReference@Headings].
+# - {Horizontal rules}[rdoc-ref:RDoc::MarkupReference@Horizontal+Rules].
+# - {Text Markup}[rdoc-ref:RDoc:MarkupReference@Text+Markup].
#
# ===== Bullet Lists
#
@@ -370,30 +396,29 @@ require 'rdoc'
# # ============Still a Heading (Level 6)
# # \== Not a Heading
#
+# A heading may contain only one type of nested block:
+#
+# - {Text Markup}[rdoc-ref:RDoc:MarkupReference@Text+Markup].
+#
# ==== Horizontal Rules
#
-# A horizontal rule begins with three or more hyphens.
+# A horizontal rule consists of a line with three or more hyphens
+# and nothing more.
#
# Example input:
#
-# # ------
-# # Stuff between.
-# #
-# # \--- Not a horizontal rule.
-# #
-# # -- Also not a horizontal rule.
-# #
-# # ---
+# ---
+# --- Not a horizontal rule.
+#
+# -- Also not a horizontal rule.
+# ---
#
# Rendered HTML:
# >>>
-# ------
-# Stuff between.
-#
-# \--- Not a horizontal rule.
+# ---
+# --- Not a horizontal rule.
#
# -- Also not a horizontal rule.
-#
# ---
#
# ==== Directives
@@ -584,83 +609,197 @@ require 'rdoc'
#
# For C code, the directive may appear in a stand-alone comment
#
-# === Text Markup
+# ==== Text Markup
#
-# Text in a paragraph, list item (any type), or heading
-# may have markup formatting.
+# Text markup is metatext that marks text as:
#
-# ==== Italic
+# - Italic.
+# - Bold.
+# - Monofont.
#
-# A single word may be italicized by prefixed and suffixed underscores.
+# Text markup may contain only one type of nested block:
#
-# Examples:
+# - More text markup:
+# italic, bold, monofont.
#
-# # _Word_ in paragraph.
-# # - _Word_ in bullet list item.
-# # 1. _Word_ in numbered list item.
-# # a. _Word_ in lettered list item.
-# # [_word_] _Word_ in labeled list item.
-# # ====== _Word_ in heading
+# ===== Italic
#
-# Any text may be italicized via HTML tag +i+ or +em+.
+# Text may be marked as italic via HTML tag or .
#
-# Examples:
+# Example input:
#
-# # Two words in paragraph.
-# # - Two words in bullet list item.
-# # 1. Two words in numbered list item.
-# # a. Two words in lettered list item.
-# # [Two words] Two words in labeled list item.
-# # ====== Two words in heading
+# Two words in a paragraph.
#
-# ==== Bold
+# >>>
+# Two words in a block quote.
#
-# A single word may be made bold by prefixed and suffixed asterisks.
+# - Two words in a bullet list item.
#
-# Examples:
+# ====== Two words in a Heading
#
-# # *Word* in paragraph.
-# # - *Word* in bullet list item.
-# # 1. *Word* in numbered list item.
-# # a. *Word* in lettered list item.
-# # [*word*] *Word* in labeled list item.
-# # ====== *Word* in heading
+# Italicized passage containing *bold* and +monofont+.
#
-# Any text may be made bold via HTML tag +b+.
+# Rendered HTML:
+# >>>
+# Two words in a paragraph.
#
-# Examples:
+# >>>
+# Two words in a block quote.
#
-# # Two words in paragraph.
-# # - Two words in bullet list item.
-# # 1. Two words in numbered list item.
-# # a. Two words in lettered list item.
-# # [Two words] Two words in labeled list item.
-# # ====== Two words in heading
+# - Two words in a bullet list item.
#
-# ==== Monofont
+# ====== Two words in a Heading
#
-# A single word may be made monofont -- sometimes called "typewriter font" --
-# by prefixed and suffixed plus-signs.
+# Italicized passage containing *bold* and +monofont+.
#
-# Examples:
+# A single word may be italicized via a shorthand:
+# prefixed and suffixed underscores.
#
-# # +Word+ in paragraph.
-# # - +Word+ in bullet list item.
-# # 1. +Word+ in numbered list item.
-# # a. +Word+ in lettered list item.
-# # [+word+] +Word+ in labeled list item.
-# # ====== +Word+ in heading
+# Example input:
#
-# Any text may be made monofont via HTML tag +tt+ or +code+.
+# _Word_ in a paragraph.
#
-# Examples:
+# >>>
+# _Word_ in a block quote.
#
-# # Two words in paragraph.
-# # - Two words in bullet list item.
-# # 1. Two words in numbered list item.
-# # a. Two words in lettered list item.
-# # [Two words] Two words in labeled list item.
-# # ====== Two words in heading
+# - _Word_ in a bullet list item.
+#
+# [_word_] _Word_ in a labeled list item.
+#
+# ====== _Word_ in a Heading
+#
+# Rendered HTML:
+# >>>
+# _Word_ in a paragraph.
+#
+# >>>
+# _Word_ in a block quote.
+#
+# - _Word_ in a bullet list item.
+#
+# [_word_] _Word_ in a labeled list item.
+#
+# ====== _Word_ in a Heading
+#
+# ===== Bold
+#
+# Text may be marked as bold via HTML tag .
+#
+# Example input:
+#
+# Two words in a paragraph.
+#
+# >>>
+# Two words in a block quote.
+#
+# - Two words in a bullet list item.
+#
+# ====== Two words in a Heading
+#
+# Bold passage containing _italics_ and +monofont+.
+#
+# Rendered HTML:
+#
+# >>>
+# Two words in a paragraph.
+#
+# >>>
+# Two words in a block quote.
+#
+# - Two words in a bullet list item.
+#
+# ====== Two words in a Heading
+#
+# Bold passage containing _italics_ and +monofont+.
+#
+# A single word may be made bold via a shorthand:
+# prefixed and suffixed asterisks.
+#
+# Example input:
+#
+# *Word* in a paragraph.
+#
+# >>>
+# *Word* in a block quote.
+#
+# - *Word* in a bullet list item.
+#
+# [*word*] *Word* in a labeled list item.
+#
+# ===== *Word* in a Heading
+#
+# Rendered HTML:
+#
+# >>>
+# *Word* in a paragraph.
+#
+# >>>
+# *Word* in a block quote.
+#
+# - *Word* in a bullet list item.
+#
+# [*word*] *Word* in a labeled list item.
+#
+# ===== *Word* in a Heading
+#
+# ===== Monofont
+#
+# Text may be marked as monofont
+# -- sometimes called 'typewriter font' --
+# via HTML tag or
.
+#
+# Example input:
+#
+# Two words in a paragraph.
+#
+# >>>
+# Two words in a block quote.
+#
+# - Two words in a bullet list item.
+#
+# ====== Two words in heading
+#
+# Monofont passage containing _italics_ and *bold*.
+#
+# Rendered HTML:
+#
+# >>>
+# Two words in a paragraph.
+#
+# >>>
+# Two words in a block quote.
+#
+# - Two words in a bullet list item.
+#
+# ====== Two words in heading
+#
+# Monofont passage containing _italics_ and *bold*.
+#
+# A single word may be made monofont by a shorthand:
+# prefixed and suffixed plus-signs.
+#
+# Example input:
+#
+# +Word+ in a paragraph.
+#
+# >>>
+# +Word+ in a block quote.
+#
+# - +Word+ in a bullet list item.
+#
+# ====== +Word+ in a Heading
+#
+# Rendered HTML:
+#
+# >>>
+# +Word+ in a paragraph.
+#
+# >>>
+# +Word+ in a block quote.
+#
+# - +Word+ in a bullet list item.
+#
+# ====== +Word+ in a Heading
#
# ==== Escaping Text Markup
#