UB player "sits out" nearly entire tourney, doesn't blind out.

[Jimbo]

If all UB did was move everyone up one place in the money it is still not equitable. A circumstance could have easily arisen in the tournament where the mystery players' ante or blind in a pot could have prevented an all-in player from being knocked out if he was up against an equal or just a tiny bit larger stack if he had the extra chip or two he would have won from the mystery player in an earlier pot.

Jimbo