Is it at all possible to have a little alert sound for when new messages are posted in the group comm?

if you literally mean group comm, you need to talk to FB about that...
I'm guessing legion comm? I don't feel it's needed, but as long as you can mute it I won't oppose it. Feel it's a waste of program time thou, so -0.5 in that aspect

Yeah... Any sort of sound alert would be annoying and a waste of time.

Lol, chatty legions would sound like a pinball arcade

It's nice in theory, however, it would be a waste, because:

A. Chat has a tendency to lag, which is why FB chat is much more viable option.
B. It doesn't really affect that many players.
C. I can't think of a C.