[css2.1] Comments within url() tokens

There are longstanding bugs against Mozilla (since at least 2006) which
presume that comments are allowed to appear within whitespace within a
URI token; that is, this is a valid URI token:

 url( /**/ http://example.com/ /**/ )

I do not see text licensing this in CSS2.1.  Both the core (4.1.1) and
the appendix G tokenization rules for URI permit only {w} between the
parentheses and the text of the URL (whether or not quoted). Section
4.3.4 says "optional whitespace" is allowed, and defines "whitespace"
by reference as the S terminal, which does not include comments.

I suspect that for interoperability's sake comments ought to be
allowed...

zw