One thing to note is that @-replying might be going to look awkward, e.g. if you type a comment (or chat message reply) it will autocomplete to
@CBBailey(they/them). The system could for these cases omit the part between parentheses but I'm sure such a feature would be abused one way or another.
I can't offer a solution to this question, but I do have a workaround.
Since this situation comes up most often in Chat, I've written a userscript, Pronoun Assistant, which automatically pulls pronoun information from the user's chat profile into the list of signatures on the left of the page:
It has since been expanded to the regular Q&A pages, since many users started stating their pronouns in their Q&A profile too. It works on questions, answers and comments.