I have had mine now for over 4 years and my reef along with a CB angle and every now and then it will nip a coral to see if its food but then moves on because its not, never any damage. But, thats just mine. I have heard different stories about them.
I have a flame back and is probably my favorite fish. He will take a nip at my Xenia once in a while but I think its more out of curiosity than any feeding. Basically the fish takes nips at something every few feet it swims, mostly LR. I have never seen any outright damage to any of my corals from him.