If you want to moderate SOME people why wouldn't this work?  (This
assumes, that you are TELLING the people that they are being put on
'read only' status):
 
Setup a new list called xxxxPOST as a moderated list, with all
  'read only' subscribed to it and set to NOMAIL.  Also add the
   main list as a member, set to MAIL.
Leave the 'read only' people in the main list but add them to the
  filter so that they won't be able to post.
Tell people who are 'read only' that they must post their messages
  via xxxxPOST.
Once the moderator 'clears' messages to xxxxPOST they will go to
  the only subscriber set to MAIL -- the main list -- and then be
  distributed to all.
 
Cheers,
  --Tom Robb, Owner, TESLJB-L, TESLHELP
 
 
    /Thomas N. Robb, Ph.D.                  [log in to unmask]\
   < Prof, Fac. of For'n Languages        [log in to unmask] >
    \Kyoto Sangyo University                +81-720-44-7303 (Fax)/