Even though (PS) and ]pS[ use the same letters, I think they're visually different enough to distinguish between the two. If they had a tag like )pS(, then it might appear to be more deliberate tag theft / spoofing, but with all the 1 and 2 letter clan tags around, there are bound to be tags that use the same letters, especially if clans from other games want to move over and add paintball2 divisions.
Currently the login system matches exact clan tags, so (PS) and ]pS[ could both be registered. Even if I were to limit tags to just alphanumerics, people would probably still try to find ways to spoof: ]p5[, ]p$[, ch|ll, 2OID, etc. I think the best thing to do is deal with these on a case by case basis and create a list of reserved tags that can't be used or registered.