The betazoid leader was deaf. The other betazoids (outside of his family) only used ASL when communicating with him. Both of his children used ASL when talking with him, and with each other. It's only about being able to communicate with the betazoid leader, and the two siblings used it with each other out of familial habit.I mean, it might really be all about their deaf leader, but I wonder if that psychic shield might also come at a prize to the Betazoid telepathic abilities.
They definitely need ways to communicate non-telepathically if they are also protecting several non-Betazoid worlds. Unless those all happen to be species with psychic abilities.
I was surprised that the Betazoid brother joined the Academy. I expected the characters to be one-time deals. So we might learn even more about the Betazoids, and possibly the War College.
It's Star Trek being inclusive, that's it. I thought it was pretty cool.

