By tag option, do you mean like on CnCalc.org (Chinese TI website) where you can flag your new topics as TI-83+, Nspire, game, etc or like Youtube vid tags? That could be handy when people are seeking for specific discussions, but unfortunately not many people might use it unless admins forced everyone to use at least 1 tag per topic.

That would probably be abused quite a lot if certain immature users signed up though. Perhaps it would need to be restricted to moderators like on yAronet (over there they use !call <nickname> to notify that an user is wanted in a topic)