I'm up to act 3 now and haven't seen the companions interact with each other a single time. That's extremely lazy
They talk to each other pretty often, both in dialogue and in exploration quips?
I haven't seen this at all. Maybe I just chose companions that don't talk to each other much? I was using Karlach, Shadowheart, and Astarion up until I got Jaheira and dropped Karlach.
Since redditors and Larian forum users nearly don't waste the same amount of time sperging about niggas and fags in the game, the most deep delving into the issues of BG3 are to be found there (which also speaks volumes about the decline the codex has gone through since it's beginning, because this would've been the stuff that would surface first here back in the day. Now it's all copy-paste from twitter and reddit).
And one of the main problems seems to be that companion banter in and out dialouge is so much RNG based, that you will never hear all of it in one playthrough ... or ever. With the bugginess of act 3 taken into account, we might see more of that with future patches.
The current consensus is that most players want their companions to chime in whenever given the chance instead of the current iteration where you have to play the game 10 times to hopefully catch all the dialogues. Which is a stupid concept to begin with in a 70+ hour game.