Minor wording changes for PEP 685 (#2448)

pep-0685.rst

@@ -27,7 +27,7 @@ The `Provides-Extra`_ core metadata specification states that an extra's
 name "must be a valid Python identifier".
 :pep:`508` specifies that the value of an ``extra`` marker may contain a
 letter, digit, or any one of ``.``, ``-``, or ``_`` after the initial character.
-Otherwise, there is no other `PyPA specification
+There is no other `PyPA specification
 <https://packaging.python.org/en/latest/specifications/>`_
 which outlines how extra names should be written or normalized for comparison.
 Due to the amount of packaging-related code in existence,
@@ -60,7 +60,7 @@ via::
     re.sub(r'[^A-Za-z0-9-.]+', '_', name).lower()
 
 The use of an underscore/``_`` differs from PEP 503's use of a hyphen/``-``,
-and it also normalizes characters outside of those allowed by :pep`508`.
+and it also normalizes characters outside of those allowed by :pep:`508`.
 Runs of ``.`` and ``-``, unlike PEP 503, do **not** get normalized to one ``_``,
 e.g. ``..`` stays the same. To note, this is inconsistent with this function's
 docstring, which *does* specify that all non-alphanumeric characters
@@ -96,10 +96,10 @@ Tools generating metadata MUST raise an error if a user specified
 two or more extra names which would normalize to the same name.
 Tools generating metadata MUST raise an error if an invalid extra
 name is provided as appropriate for the specified core metadata version.
-If an older core metadata version is specified and the name would be
+If a project's metadata specifies an older core metadata version and the name would be
 invalid with newer core metadata versions,
-tools SHOULD warn the user.
-Tools SHOULD warn users when an invalid extra name is read and SHOULD not use
+tools reading that metadata SHOULD warn the user.
+Tools SHOULD warn users when an invalid extra name is read and SHOULD ignore
 the name to avoid ambiguity.
 Tools MAY raise an error instead of a warning when reading an
 invalid name, if they so desire.