Disputed premise, not circular reasoning

It's sometimes seemed inelegant to me that that using the conclusion in the premise is automatically invalid. Why is this? It seems like a special case.

Actually it's not that there's a special case against using the conclusion in the premise, it's that the point of argument is to show that the opposing position is irrational, and the opposing position is only irrational if information *available to the person who holds it* contradicts it. So I wish people wouldn't talk about "circular reasoning" but "disputed premise", because that's the more general form of the fallacy. Talking about it as it's limited to using the conclusion in the premise opens a door to people making arguments that take *other* disputed premises for granted, and claiming it's not circular reasoning because the conclusion isn't in the premise (a different disputed claim is).