This situation came up earlier tonight.

Professor X, Worlds Most Powerful Telepath exhausts Airwalker. Then Mimic (copying Prof X) attempted to use his ability again on the same Air Walker.

I know this used to be a legal move, but somebody mentioned that the wording in the new rules(as of MTU) stated you can't target a character with an exhaust effect if it was already exhausted.

Is this true and could you quote or link the page I could find this info

There is no restriction on the target except that it cost 5 or less. If it doesn't say target ready character you can target an exhausted character. The exhaust is part of the effect meaning it will attempt to resolve as much of the effect as possible. If it can't exhaust the character, then it moves on to the next part, the burn.

There has been no change in the targeting rules. The part of the FAQ that probably confused this other person is text pertaining to how Substitute works.

-Mike