Update comparison rules for version and string markers

Clarify comparison rules for version and string markers in dependency specifiers.

Author: henryiii

source/specifications/dependency-specifiers.rst

@@ -197,23 +197,24 @@ vulnerability. Markers were first standardised in :pep:`345`. This document
 fixes some issues that were observed in the design described in :pep:`426`.
 
 Comparisons in marker expressions are based on the types in the table below.
-The types marked with ``Version`` or ``Version | String`` use the version
+The variables marked with ``Version`` or ``Version | String`` use the version
 comparison rules of the :ref:`Version specifier specification
 <version-specifiers>` when those are defined (that is when both sides have a
 valid version specifier). If both sides are not expressible as a ``Version``,
 then ``==``, ``>=``, and ``<=`` check for exact equality; no ordering is
-assumed. On the other values, operators perform the same as they do for strings
+assumed. On other operators, operators perform the same as they do for strings
 or sets in Python based on whether the marker value is a string or set itself.
 Otherwise an error should be raised. e.g. the following will result in errors::
 
     "dog" ~= "fred"
     python_version ~= "surprise"
 
-Values that are marked as ``String`` may also follow same rules as ``Version``
-defined above, with ``>=`` and ``<=`` being equivalent to ``==``, and ``<`` and
-``>`` always evaluating to ``False``. This is legacy behavior due to an older
-version of this spec, and tools may choose to warn or fail if these are used on
-strings.
+Variables that are marked solely as ``String`` support `==` and `!=`; ordered
+comparison operators may also follow same rules as ``Version`` defined above
+when not a valid Version, with ``>=`` and ``<=`` being equivalent to ``==``,
+and ``<`` and ``>`` always evaluating to ``False``. This is legacy behavior
+due to an older version of this spec, and tools may choose to warn or fail
+if orderd comparisons are used on ``String`` markers.
 
 User supplied constants are always encoded as strings with either ``'`` or
 ``"`` quote marks. Note that backslash escapes are not defined, but existing