Something else that you could do is what we do on the Rugbyrefs forum.
New members are given an "L" plate as an avatar and cannot change it until they move into the Registered Members group. This makes it immediately obvious to everyone there is a NKOTB.
New Members have to make 10 posts before they lose the L Plate, unless they are moved into the Registered Members group before that by an Admin
(We a have a "Referees only" section, and you cannot get into unless you can show that you are a bona fide Referees Society/Association member)