A good commit message doesn't need symbols to tell you what it is doing. (And no, I don't write perfect commit messages.)
> Once we’re there, how is it better to use things like Chinese characters rather than emojis?
Because there are quite a lot of people in this world who speak Chinese but not English, while nobody speaks only emoji.
> On balance, it is better that they are supported properly even if you personally dislike them.
To be clear, I'm not against emoji or Unicode in general. I just dislike the way they seem to be showing up in commit messages and the like as attributes.