Apply suggestions from code review

Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>

Author: zklaus

peps/pep-0780.rst

@@ -165,7 +165,7 @@ library as ``sys.abi_features``, and as the new environment marker variable
 ``sys_abi_features``.
 
 ABI Features
-''''''''''''
+------------
 
 ABI features are intrinsic properties of the Python interpreter, expressed as
 simple, understandable strings.
@@ -199,8 +199,8 @@ which case there MUST be at most one feature present.
     this feature MUST NOT be present.
 
 
-Addition to the Python Standard Library
-'''''''''''''''''''''''''''''''''''''''
+The :data:`!sys.abi_features` attribute
+---------------------------------------
 
 Making the ABI features available in an easily accessible, expressive,
 standardized way is useful beyond the scope of environment markers.
@@ -224,8 +224,8 @@ defined in this PEP or in a subsequent PEP.
 An example value would be ``sys.abi_features == frozenset({"free-threading",
 "debug", "32-bit"})`` on a free-threaded debug build for win32.
 
-Environment Markers
-'''''''''''''''''''
+``sys_abi_features`` environment marker
+---------------------------------------
 
 To make ABI features available in dependency specifications, a new environment
 marker variable, ``sys_abi_features``, is added to the format of dependency
@@ -258,7 +258,8 @@ Like the grammar, also the overview table of environment markers in
       - Sample values
     * - ``sys_abi_features``
       - ``sys.abi_features`` [#sys-abi-features]_
-      - ``set()``, ``{"free-threading"}``, ``{"free-threading", "debug"}``
+      - ``frozenset()``, ``frozenset({'free-threading', '64-bit'})``,
+        ``frozenset({'gil-enabled', 'debug', '32-bit'})``
 
 With these additions, ABI features can be used in dependency specifications via
 the ``in`` operator to test for the presence of a feature, or the ``not in``
@@ -361,11 +362,11 @@ of the ``packaging`` library at `Environment markers for ABI features
 also available.
 
 Since ``pip`` uses a vendored copy of ``packaging`` internally, we also provide
-`a patched version of pip
-<https://github.com/zklaus/pip/tree/env-marker-free-threading>`__, which is
-based on pypa/pip:main with the vendored ``packaging`` replaced by the
+`a patched version of pip`__, which replaces the vendored ``packaging`` with the
 reference implementation linked above.
 
+__ https://github.com/zklaus/pip/tree/env-marker-free-threading
+
 Rejected Ideas
 ==============