Comments from PR review, improve phrasing

Author: matthieucan

Lib/email/_header_value_parser.py

@@ -2404,13 +2404,12 @@ def get_section(value):
                                         value))
     section.append(ValueTerminal('*', 'section-marker'))
     value = value[1:]
-    # We don't use str.isdigit because only 0-9 are accepted, not super-script
-    # and other types of digits.
-    if not value or not '0' <= value[0] <= '9':
+    # We don't use str.isdigit because only ASCII digits are allowed.
+    if not value or not ('0' <= value[0] <= '9'):
         raise errors.HeaderParseError("Expected section number but "
                                       "found {}".format(value))
     digits = ''
-    while value and '0' <= value[0] <= '9':
+    while value and ('0' <= value[0] <= '9'):
         digits += value[0]
         value = value[1:]
     if digits[0] == '0' and digits != '0':

Lib/test/test_email/test__header_value_parser.py

@@ -2983,8 +2983,7 @@ def mime_parameters_as_value(self,
             [('r', '"')],
             [errors.InvalidHeaderDefect]*2),
 
-        # gh-87112: Unicode super-script digits (and others) are not allowed
-        # as section numbers.
+        # gh-87112: Only ASCII digits can be section numbers.
         'non_allowed_digits': (
             'foo*0=bar; foo*²=baz',
             ' foo="bar"',