I have noticed this couple of times, I can’t reply to users from kbin.social. The loader keeps spinning, and if you refresh, the reply doesn’t show.

Is this a known issue, or just some random network / system load issue?

Solution (also posted as a comment below) Select ‘English’ as the language for the reply, otherwise it won’t post to any instance that doesn’t have ‘undetermined’ in the languages or to kbin.social account.