They may simply be a person with some experience on LISTSERV(tm) hosted
lists, and have their preferences for how they like to do things.  More
important to your situation, I think, is based on other information you
have about the prospective subscriber- do they "belong" in the audience
your list is intended for?  I wouldn't use their apparent technical
familiarity with the software product as a basis for judgement.

Many people have acquired a fondness for CONCEAL from the times when
list "harvesting" was often done and used to populate spam databases. 
These days most every list owner uses Review=Owner (as already mentioned
by Rich) to prevent the harvesting and make the use of Conceal
irrelevant - but old habits often linger.  I can't read much psychology
from the choice of header style, and the noack/norepro just means that
if they should post to the list, they don't want a confirmation of
distribution, or a copy of their own message.... not much psychology
there either.

Since you describe your list as announcement-oriented,
Default-options=review or nopost may already be in place... or if you're
concerned this prospective subscriber might be disruptive, you can
quietly set review or nopost on them once they are subscribed.

>>> [log in to unmask] 9/20/2006 12:22:48 PM >>>
One of the lists for which I am a moderator received an unusual request
to
join today, and I wondered if anyone here had any ideas on whether it
sounds
off to them (I am a real Listserv newbie, just learning my way
around).

Normally, people who join our lists don't make special requests, but
this
person made the following settings requests: FULLHDR, NOACK, NOREPRO,
CONCEAL.

So they want to see full headers, and they don't want any sort of
acknowledgment sent to them regarding any messages they send, and they
don't
want their presence to be revealed to the other members (although
owners can
always see who is subscribed, of course).

What's odd about this is that our list is pretty exclusively an
announcements-only list -- in other words, people who belong to the
list
don't post (although they can) and the only posts to the list are by
the
owners sending out information about upcoming events or news items.

I'd appreciate any feedback from the lot of experts here on whether we
should approve this request or not.

J