NOTE: This would suggest a surface reading of Brandom's "deontic scorekeeping" might be keeping score of who has what obligations, who is following or breaking rules, etc.

Then the argument against LLMs being party to that is that we don't really assign roles and responsibilities to LLMs, they don't really have "duties" or "obligations" in the way a member of society will have. We don't negotiate with them over who should do what, they don't contribute to the rules that are set for them.

I'm literally just guessing based on the context here though, since the few times I've tried to watch podcasts with Brandom I generally bounce after 15-20 minutes feeling I haven't really understood anything he is saying.

Mathematicians always define their terms exactly, in order to begin their discussion. Philosophers never define their terms exactly, because then they would have nothing to discuss.