Nemo used to have a full grown emperor a Angel in his sps reef for quite a while with no problems, although I do think he has a taste for lps. I personally would never add one to my reef, I like my corals too much to chance it.... and the odds of it not nipping coral is about the odds of buying a fat healthy copperband that eats flakes/pellets, which is to say not impossible, but AL s o not very probable.
That of course is just my 2cents