Valdis,
   Many systems, such as UN*X, have central bulletin boards, or user
accessable files, containing such various digests.  These are usually
subscribed to directly.  Since LISTSERV has a logging facility, just
use that as an excuse to get LISTSERV on the other list.  Now, who's
gonna be the wiser if some user just does their own SUBSCRIBE?
 
A nasty alternative is send a note to the guy and say that you are going
to drop your secret redistribution effective very very soon.  Then make
about 400 fake userids, and have each one send a subscription to that
list.  You, I, and *MAYBE* he, knows this could very well spell the end
of that list altogether, due to the massive load.  Of course I don't mean
for you to seriously do this, but the matter is getting out of hand to the
degree that network andimistrators might want to cut off such lists.
Especially lists like SF-lovers, which don't really contribute to the
computing functions of the members of the networks.  If any list has to
go out, those are likely to be first, due to their "unimportance".
He really should be keeping a lower profile, and minimize his impact.