I think the problem with characters may well be that there is a limit on the numerical length which wasn't there before.

eg hash codes under (say) 1000. Greek seems to end with omega ώ (974) above 1000 it is Cyrillic like Ж

because the preview is controlled by your browser it looks OK. But once stored by Mudcat it is controlled elsewhere.

If the above posts correctly - I would posit a higher number like 9999 maybe - where the emojis live. Having said that I managed (and got a reaction that confirmed) to get emojis to post, that didn't a day later so either the threshold is variable from some bug, or max it still tinkering.