If it were up to me, anything outside the basic character set in a source file would be a syntax error, I'm simply reporting what the spec says.
And yeah, the chinese tone in practice does not align with the idea of "down a little up a lot" either. It depends on context...
I still don't want anything as unpredictable as Unicode in my code. How many different encodings will display as the same variable name and how is the compiler supposed to decide?
If you're thinking of comments and user facing strings, the OP already excluded those.