Comment-URL question

Reading through the current thread of mail messages
on including a comment URL as an attribute to a cookie,
I find I cannot determine whether there is any
limitation on the location of the comment URL.  In
other words, does the comment URL need to be on the
same server as the resource producing the cooking
about which it comments?

If not, does the server on which it resides need to
domain-match the server from which the cookie is
produced?

I raise these issues because there are a number of
error conditions which can arise when the comment
URL does not reside on the same server which do not
otherwise come into play, and I am concerned with
the complexity that handling those error conditions
raises.
		regards,
			Ted Hardie
			NASA NIC