that does seem odd, blennies are weird fish. mine loves to dig up my sand on one side of the tank, seemingly to make a cave for himself or something
i think i've seen that some people report bicolor blennies to be nippy, and they're the same genus as midas blennies so seems possible it's going after coral
Just caught my golden midas blenny that I've had for over a year go ham on a hammer coral... ughhhh I loved my golden midas but I can't have him eating coral. :/