Reactions do not handle unicode ligatures
Trying to react with a ligatured character like ⑨ or some family emojis (composed of multiple single characters) gives an answer 500
I think it takes ligatures as separated characters, I can see them being a problem as they are shown as multiple characters when using a font that doesn't support them.
I don't know if they should be considered a single character but I really want to react with ⑨ ;-;
man unicode
at Combining characters
Unicode equivalence