[over.oper]p3 says:

The following operators cannot be overloaded:
. .* :: ?:
nor can the preprocessing symbols # (15.6.2) and ## (15.6.3).

This has no normative content (this is implied by the definition of the grammar term operator not including these), and lacks the technical precision we'd expect from normative wording, in that "operator" is not formally defined other than by the grammar term operator (which, as noted, excludes these operators). We should convert this into a note.