I've been thinking about this more and am very concerned about this. Gail Damerow gives directions in her books on how to thaw the comb then says to put on neosporin and keep them separated from the others so that they don't do more damage to it.
I am pretty gun-shy about how or what to do in a case like this....
I am no expert on frostbite but a totally black comb sounds like it may require emergency measures. If he were mine I would probably try to find a vet to advise me on what - if anything - to do in this case.
Just throwig a little reminder out there. When using neosporin on a chicken always make sure you get the kind that DOESNT have pain relief