Several years ago, a close friend who is profoundly hard of hearing, asked my assistance in making arrangements for air travel on UAL, which of course I was happy to do. He specifically asked that UAL be aware he was nearly Deaf, as he appreciated early boarding and other such considerations.

Not only did UAL extend such requested courtesies, they assigned a f/a who was fluent in sign language to work the section where he was seated, and she signed the safety demo and pertinent announcements specifically for my friend, who was deeply appreciative!

Anyway, to answer the question of this thread, yes, I have seen deaf pax on planes from time to time. In those cases, I don't seem to recall any special treatment like that extended to my friend...the deaf pax simply blended in with everyone else.