I've heard the same thing - some folks say yes others say no.
I've got a flame in my 55 reef and all is well. Has not nipped at any corals, been in there about 6 months now.
Others may have different opinions.
Brian
I have had my flame angel in a reef for over four years without a problem but I have seen others that eat leather coals and polyps. IMHO take a chance on a small one and keep it fed. Then watch it closely to see if it starts nipping at any corals.
SiF