In our repos, we have some basic stuff like ruff that runs, and that includes a hard error on any Unicode characters. We mostly did this after some un-fun times when byte order marks somehow ended up in a file and it made something fail.

I have considered allowing a short list that does not include emojis, joining characters, and so on - basically just currency symbols, accent marks, and everything else you'd find in CP-1521 but never got around to it.