In the chat, Monica was asked many times, by many other moderators, to please use "singular they" for people who she actively knew preferred that pronoun. Monica flat out refused, saying it was confusing and grammatically incorrect. She said she'd be happy to use literally any other word, including "new" pronouns like "Xe". She also suggested that she could avoid using pronouns altogether, either just for people who preferred singular they, or universally for everyone. (Other moderators said this last option likely would have been fine had Monica not made known her reason for doing so.)
Now, on a purely personal level, I also find singular they to be super confusing in conversation, at least when the subject is unambiguous. But the extent to which Monica refused to budge, even after being told that she was making colleagues uncomfortable, struck me as behavior that would need to be disciplined in any formal workplace.