It really doesn't matter to me, if they really want to do it there is very little that can be done agaisn't it.
The fact is that if someone is impersonating your staff, there must be a reason, nobody do something for no reason. Most players will threat you as you threat them, if you talk like you were god and disrespectful with everyone, they will react the same way with you.
Although, some people don't have any reason to do it so, or very little reason, those that wants just to see the people angry or sad(AKA Agent of Chaos), so yea, those you have to IP ban or simply ignore if he found a good way to be unbanned.
(Why would a clown act if there is no one seem to care about him, he'll just bore out and stop.)
But if you're really being abused a lot of times, Zairick option is really the best, but I wouldn't ever do it, Too much working ( I'm lazy, sue me).