CopperBanded (rostratus), Marginalis and Long Nosed (forcipiger) all do well in reefs. They generally don't bother the corals you purchase, but will enjoy small inverts such as tube worms.
The Raops family of butterflies are all deep water and include the declivus, tinkerii, burgess, flavocoronatus and mitratus. These butterflys may be reef safe, but there is nothing to prevent them from developing a taste for one of your prized corals. The premise that they are deep water and therefore wont eat your corals is possible, but not guaranteed.
I had a declivus several years ago in my reef.... he completely denuded the tank of all polyps and zoas. But to me, he was worth it!
-Rob