I have a yellow coris, and he doesn't show any interest in any corals, but I don't have any feather dusters. My copperband keeps those little white tube worms wiped out. I have seen the yellow coris eat a bristle worm though, which I was glad to see. I don't mind a few of them, but don't want to be overrun with them.
The yellow coris gets along well with everything else in the tank, doesn't chase anything and doesn't get picked on either. I haven't noticed any vermetid snails in the tank, but I do know I have a few in my frag tank, and they're that big ones, not the little bitty ones. I've even tried auirting vinegar into the tube with a syringe and it doesn't seem to do anything to them. I'm about ready to just go smash their shells and get rid of them that way.