Sometimes the best way to tell if someone has more than one alias is to check the two (or three, or four, etc.) people's typing habits. Usually if they are in the same post they will agree, and you can tell by their grammar. (If two people's grammar is absolutely horrible and their spelling is just as bad they are probably the same person.) Also a wonderful way is capitilization. Some people capitalize their user name only, others capitalize correctly, and others capitalize nothing at all. And lastly you can tell by the quality of their posts. If they actually post things worthy of discussion that's one person, but another may make useless joke posts and such. Some people ONLY do that. That way you can narrow it all down. Oh, and you can check their attitude. If two people are unusually creative and love to post big discussion threads, they may be the same person. If two people say "What the heck did you post this for? Who cares?!", then that's probably the same person. Or, you could just check and see if their e-mail is the same.... :)
-YOSHI :P