askvortsov if tags can't join the party that is okay. What we see is if the feature is in core it will be automatically taken care by the team. I know in a way it's a burden to the theme. If extension is a easy solution in terms of dev friendly .. let us go with extension. Both flarumates and Dev's will be happy.
I don't think why this can not be in core, because flarum can support utf8 out of the box and if needed admin can set it to unicode in the settings panel (like we change settings for usernames ID/full name)
Again go with whichever is easier to Dev's and future proof.