wm-bot does not appear to be logging in UTF-8.
What I sent:
[22:50:59] <AntiComposite> # Here are some umlauted vowels: öäü [22:51:01] <AntiComposite> # Here is a deck of cards: ♠♣♥♦
What got logged:
[02:50:59] <AntiComposite> # Here are some umlauted vowels: öäü [02:51:02] <AntiComposite> # Here is a deck of cards: ♠♣♥♦
https://wm-bot.wmflabs.org/libera_logs/%23wm-bot/20210824.txt
This has happened in other channels as well, and with messages sent by others.