I really don't know if it will hurt anything or not(?)I had concerns with locking in moisture too, I wasn't certain if there was negative effects to locking in Moisture. Maybe just covering the tips where the frostbite is more likely is a good idea. Tomorrow we have a warm spell starting and I will be cleaning it off the roosters I used it on.
If you normally do get frostbitten combs, then it's worth a try to see if the vaseline works. Maybe on a couple roosters and compare?