PEP 622: Explain why * and ... don't make good wildcards

(And hint that ? is a little better but still worse than _.)

pep-0622.rst

@@ -1425,6 +1425,38 @@ legitimate use for ``_`` as an important global variable, esp. in
 i18n) and the only reason for this prohibition was to prevent some
 user confusion.  But it's not the hill to die on.
 
+Use some other token as wildcard
+--------------------------------
+
+It has been proposed to use ``...`` (i.e., the ellipsis token) or
+``*`` (star) as a wildcard.  However, both these look as if an
+arbitrary number of items is omitted::
+
+    case [a, ..., z]: ...
+    case [a, *, z]: ...
+
+Both look like the would match a sequence of at two or more items,
+capturing the first and last values.
+
+In addition, if ``*`` were to be used as the wildcard character, we
+would have to come up with some other way to capture the rest of a
+sequence, currently spelled like this::
+
+    case [first, second, *rest]: ...
+
+Using an ellipsis would also be more confusing in documentation and
+examples, where ``...`` is routinely used to indicate something
+obvious or irrelevant.  (Yes, this would also be an argument against
+the other uses of ``...`` in Python, but that water is already under
+the bridge.)
+
+Another proposal was to use ``?``.  This could be acceptable, although
+it would require modifying the tokenizer.  But ``_`` is already used
+as a throwaway target in other contexts, and this use is pretty
+similar.  This example is from ``difflib.py`` in the stdlib::
+
+  for tag, _, _, j1, j2 in group: ...
+
 
 .. _deferred ideas: