diff --git a/mercurial/commands.py b/mercurial/commands.py
--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -4593,12 +4593,15 @@ def help_(ui, name=None, **opts):
     section = None
     subtopic = None
     if name and '.' in name:
-        name, section = name.split('.', 1)
-        section = encoding.lower(section)
-        if '.' in section:
-            subtopic, section = section.split('.', 1)
+        name, remaining = name.split('.', 1)
+        remaining = encoding.lower(remaining)
+        if '.' in remaining:
+            subtopic, section = remaining.split('.', 1)
         else:
-            subtopic = section
+            if name in help.subtopics:
+                subtopic = remaining
+            else:
+                section = remaining
 
     text = help.help_(ui, name, subtopic=subtopic, **opts)
 
diff --git a/mercurial/help.py b/mercurial/help.py
--- a/mercurial/help.py
+++ b/mercurial/help.py
@@ -184,13 +184,13 @@ def loaddoc(topic, subdir=None):
     return loader
 
 internalstable = sorted([
-    (['bundles'], _('container for exchange of repository data'),
+    (['bundles'], _('Bundles'),
      loaddoc('bundles', subdir='internals')),
-    (['changegroups'], _('representation of revlog data'),
+    (['changegroups'], _('Changegroups'),
      loaddoc('changegroups', subdir='internals')),
-    (['requirements'], _('repository requirements'),
+    (['requirements'], _('Repository Requirements'),
      loaddoc('requirements', subdir='internals')),
-    (['revlogs'], _('revision storage mechanism'),
+    (['revlogs'], _('Revision Logs'),
      loaddoc('revlogs', subdir='internals')),
 ])
 
diff --git a/mercurial/help/internals/bundles.txt b/mercurial/help/internals/bundles.txt
--- a/mercurial/help/internals/bundles.txt
+++ b/mercurial/help/internals/bundles.txt
@@ -1,6 +1,3 @@
-Bundles
-=======
-
 A bundle is a container for repository data.
 
 Bundles are used as standalone files as well as the interchange format
@@ -8,7 +5,7 @@ over the wire protocol used when two Mer
 each other.
 
 Headers
--------
+=======
 
 Bundles produced since Mercurial 0.7 (September 2005) have a 4 byte
 header identifying the major bundle type. The header always begins with
diff --git a/mercurial/help/internals/changegroups.txt b/mercurial/help/internals/changegroups.txt
--- a/mercurial/help/internals/changegroups.txt
+++ b/mercurial/help/internals/changegroups.txt
@@ -1,6 +1,3 @@
-Changegroups
-============
-
 Changegroups are representations of repository revlog data, specifically
 the changelog, manifest, and filelogs.
 
@@ -35,7 +32,7 @@ There is a special case chunk that has 0
 call this an *empty chunk*.
 
 Delta Groups
-------------
+============
 
 A *delta group* expresses the content of a revlog as a series of deltas,
 or patches against previous revisions.
@@ -111,21 +108,21 @@ changegroup. This allows the delta to be
 which can result in smaller deltas and more efficient encoding of data.
 
 Changeset Segment
------------------
+=================
 
 The *changeset segment* consists of a single *delta group* holding
 changelog data. It is followed by an *empty chunk* to denote the
 boundary to the *manifests segment*.
 
 Manifest Segment
-----------------
+================
 
 The *manifest segment* consists of a single *delta group* holding
 manifest data. It is followed by an *empty chunk* to denote the boundary
 to the *filelogs segment*.
 
 Filelogs Segment
-----------------
+================
 
 The *filelogs* segment consists of multiple sub-segments, each
 corresponding to an individual file whose data is being described::
@@ -154,4 +151,3 @@ Each filelog sub-segment consists of the
 
 That is, a *chunk* consisting of the filename (not terminated or padded)
 followed by N chunks constituting the *delta group* for this file.
-
diff --git a/mercurial/help/internals/requirements.txt b/mercurial/help/internals/requirements.txt
--- a/mercurial/help/internals/requirements.txt
+++ b/mercurial/help/internals/requirements.txt
@@ -1,5 +1,3 @@
-Requirements
-============
 
 Repositories contain a file (``.hg/requires``) containing a list of
 features/capabilities that are *required* for clients to interface
@@ -19,7 +17,7 @@ The following sections describe the requ
 Mercurial core distribution.
 
 revlogv1
---------
+========
 
 When present, revlogs are version 1 (RevlogNG). RevlogNG was introduced
 in 2006. The ``revlogv1`` requirement has been enabled by default
@@ -28,7 +26,7 @@ since the ``requires`` file was introduc
 If this requirement is not present, version 0 revlogs are assumed.
 
 store
------
+=====
 
 The *store* repository layout should be used.
 
@@ -36,7 +34,7 @@ This requirement has been enabled by def
 was introduced in Mercurial 0.9.2.
 
 fncache
--------
+=======
 
 The *fncache* repository layout should be used.
 
@@ -48,7 +46,7 @@ enabled (which is the default behavior).
 1.1 (released December 2008).
 
 shared
-------
+======
 
 Denotes that the store for a repository is shared from another location
 (defined by the ``.hg/sharedpath`` file).
@@ -58,7 +56,7 @@ This requirement is set when a repositor
 The requirement was added in Mercurial 1.3 (released July 2009).
 
 dotencode
----------
+=========
 
 The *dotencode* repository layout should be used.
 
@@ -70,7 +68,7 @@ is enabled (which is the default behavio
 Mercurial 1.7 (released November 2010).
 
 parentdelta
------------
+===========
 
 Denotes a revlog delta encoding format that was experimental and
 replaced by *generaldelta*. It should not be seen in the wild because
@@ -80,7 +78,7 @@ This requirement was added in Mercurial 
 1.9.
 
 generaldelta
-------------
+============
 
 Revlogs should be created with the *generaldelta* flag enabled. The
 generaldelta flag will cause deltas to be encoded against a parent
@@ -91,7 +89,7 @@ July 2011). The requirement was disabled
 default until Mercurial 3.7 (released February 2016).
 
 manifestv2
-----------
+==========
 
 Denotes that version 2 of manifests are being used.
 
@@ -100,7 +98,7 @@ May 2015). The requirement is currently 
 by default.
 
 treemanifest
-------------
+============
 
 Denotes that tree manifests are being used. Tree manifests are
 one manifest per directory (as opposed to a single flat manifest).
diff --git a/mercurial/help/internals/revlogs.txt b/mercurial/help/internals/revlogs.txt
--- a/mercurial/help/internals/revlogs.txt
+++ b/mercurial/help/internals/revlogs.txt
@@ -1,6 +1,3 @@
-Revlogs
-=======
-
 Revision logs - or *revlogs* - are an append only data structure for
 storing discrete entries, or *revisions*. They are the primary storage
 mechanism of repository data.
@@ -28,7 +25,7 @@ revision #0 and the second is revision #
 used to mean *does not exist* or *not defined*.
 
 File Format
------------
+===========
 
 A revlog begins with a 32-bit big endian integer holding version info
 and feature flags. This integer is shared with the first revision
@@ -77,7 +74,7 @@ possibly located between index entries. 
 below.
 
 RevlogNG Format
----------------
+===============
 
 RevlogNG (version 1) begins with an index describing the revisions in
 the revlog. If the ``inline`` flag is set, revision data is stored inline,
@@ -129,7 +126,7 @@ The first 4 bytes of the revlog are shar
 and the 6 byte absolute offset field from the first revlog entry.
 
 Delta Chains
-------------
+============
 
 Revision data is encoded as a chain of *chunks*. Each chain begins with
 the compressed original full text for that revision. Each subsequent
@@ -153,7 +150,7 @@ by default in Mercurial 3.7) activates t
 computed against an arbitrary revision (almost certainly a parent revision).
 
 File Storage
-------------
+============
 
 Revlogs logically consist of an index (metadata of entries) and
 revision data. This data may be stored together in a single file or in
@@ -172,7 +169,7 @@ The actual layout of revlog files on dis
 (possibly containing inline data) and a ``.d`` file holds the revision data.
 
 Revision Entries
-----------------
+================
 
 Revision entries consist of an optional 1 byte header followed by an
 encoding of the revision data. The headers are as follows:
@@ -187,7 +184,7 @@ x (0x78)
    The 0x78 value is actually the first byte of the zlib header (CMF byte).
 
 Hash Computation
-----------------
+================
 
 The hash of the revision is stored in the index and is used both as a primary
 key and for data integrity verification.
diff --git a/tests/test-help.t b/tests/test-help.t
--- a/tests/test-help.t
+++ b/tests/test-help.t
@@ -929,16 +929,16 @@ internals topic renders index of availab
   Technical implementation topics
   """""""""""""""""""""""""""""""
   
-       bundles       container for exchange of repository data
-       changegroups  representation of revlog data
-       requirements  repository requirements
-       revlogs       revision storage mechanism
+       bundles       Bundles
+       changegroups  Changegroups
+       requirements  Repository Requirements
+       revlogs       Revision Logs
 
 sub-topics can be accessed
 
   $ hg help internals.changegroups
-      Changegroups
-      ============
+  Changegroups
+  """"""""""""
   
       Changegroups are representations of repository revlog data, specifically
       the changelog, manifest, and filelogs.
@@ -974,7 +974,7 @@ sub-topics can be accessed
       this an *empty chunk*.
   
       Delta Groups
-      ------------
+      ============
   
       A *delta group* expresses the content of a revlog as a series of deltas,
       or patches against previous revisions.
@@ -1050,21 +1050,21 @@ sub-topics can be accessed
       which can result in smaller deltas and more efficient encoding of data.
   
       Changeset Segment
-      -----------------
+      =================
   
       The *changeset segment* consists of a single *delta group* holding
       changelog data. It is followed by an *empty chunk* to denote the boundary
       to the *manifests segment*.
   
       Manifest Segment
-      ----------------
+      ================
   
       The *manifest segment* consists of a single *delta group* holding manifest
       data. It is followed by an *empty chunk* to denote the boundary to the
       *filelogs segment*.
   
       Filelogs Segment
-      ----------------
+      ================
   
       The *filelogs* segment consists of multiple sub-segments, each
       corresponding to an individual file whose data is being described:
@@ -2872,28 +2872,28 @@ Sub-topic indexes rendered properly
   bundles
   </a>
   </td><td>
-  container for exchange of repository data
+  Bundles
   </td></tr>
   <tr><td>
   <a href="/help/internals.changegroups">
   changegroups
   </a>
   </td><td>
-  representation of revlog data
+  Changegroups
   </td></tr>
   <tr><td>
   <a href="/help/internals.requirements">
   requirements
   </a>
   </td><td>
-  repository requirements
+  Repository Requirements
   </td></tr>
   <tr><td>
   <a href="/help/internals.revlogs">
   revlogs
   </a>
   </td><td>
-  revision storage mechanism
+  Revision Logs
   </td></tr>
   
   
@@ -2957,8 +2957,7 @@ Sub-topic topics rendered properly
   number or hash, or <a href="/help/revsets">revset expression</a>.</div>
   </form>
   <div id="doc">
-  <h1>representation of revlog data</h1>
-  <h2>Changegroups</h2>
+  <h1>Changegroups</h1>
   <p>
   Changegroups are representations of repository revlog data, specifically
   the changelog, manifest, and filelogs.
@@ -3000,7 +2999,7 @@ Sub-topic topics rendered properly
   There is a special case chunk that has 0 length (&quot;0x00000000&quot;). We
   call this an *empty chunk*.
   </p>
-  <h3>Delta Groups</h3>
+  <h2>Delta Groups</h2>
   <p>
   A *delta group* expresses the content of a revlog as a series of deltas,
   or patches against previous revisions.
@@ -3091,19 +3090,19 @@ Sub-topic topics rendered properly
   changegroup. This allows the delta to be expressed against any parent,
   which can result in smaller deltas and more efficient encoding of data.
   </p>
-  <h3>Changeset Segment</h3>
+  <h2>Changeset Segment</h2>
   <p>
   The *changeset segment* consists of a single *delta group* holding
   changelog data. It is followed by an *empty chunk* to denote the
   boundary to the *manifests segment*.
   </p>
-  <h3>Manifest Segment</h3>
+  <h2>Manifest Segment</h2>
   <p>
   The *manifest segment* consists of a single *delta group* holding
   manifest data. It is followed by an *empty chunk* to denote the boundary
   to the *filelogs segment*.
   </p>
-  <h3>Filelogs Segment</h3>
+  <h2>Filelogs Segment</h2>
   <p>
   The *filelogs* segment consists of multiple sub-segments, each
   corresponding to an individual file whose data is being described: