Comment by ColonelPhantom

What are some cases where 'they/them/their' does not work, but 'he/him/his' does?

As for neopronouns like 'zir', I don't think I ever actually encountered anyone who uses them, either online or irl, with the exception of one Twitter user who preferred 'it'. So I mostly see them as a non-issue, although if someone does prefer a neopronoun I don't see the point of making a fuss either.