What's going on with Betazoids in Academy? [spoilers]

Why are the Betazoids described as an empathic species in Academy? Troi was an empath, but that’s because she’s half human. Lwxana and the Betazoid “delegates” in LDS are all telepathic. They all regularly use telepathy to speak to each other and to humans they’re close with. Why are the Betazoids in Academy signing to each other to communicate subtly instead of thinking?

Also, was the Betazoid president’s taking off of the speech device supposed to be symbolic of something in lore? I know the actsman is Deaf, but is there some kind of link between Deafness/muteness and the psionic wall?