When rooms get really loud, you just want it to be silent. However, every so often, when playing a game, you'd want some vital information. So if you were deafened, you can still hear the vital information you'd need. Setting up ACL is a hassle and if this function were to be added, then even the new mumble users can use this great feature. Also, not everyone can always make their own channel and set ACL, as they probably won't have sufficient privilege. This feature would be user friendly and easily accessible. Overall, this feature would really help mumble and it's growth.