Barry:
 
LISTSERV is not broken, you're user is.  On one of my
hyperactive lists, the default REPLY-TO: is the poster and
not the list since many folks (used to) reply back to the
list, instead of the poster.
 
I realize that isn't exactly what you are saying, but a
properly configured subscriber's client, with a poster and
subscriber who know what they are doing allows for this
flexibility.
 
This is especially useful for survey requests where
responses should be sent to the requestor, who then
summaries the results back to the list.
 
In a perverse sort of way, the problem user slightly
mitigated the dire results of SPAM by NOT directing
inappropriate responses back to your list.  Thus, we can
save one of the two bullets we would have used ;-)
 
Depending on your WELCOME file and other possible warnings
that you may have sent, you can UNSUB the user, set to
NOPOST, or REVIEW, or FILTER= them.
 
/Pete Weiss at Penn State