Jim J. Jewett writes:
At the time, we considered it, and we also considered a narrower restriction on using multiple scripts in the same identifier, or at least the same identifier portion (so it was OK if separated by _).
This would ban "παν語", aka "pango". That's arguably a good idea (IMO, 0.9 wink), but might make some GTK/GNOME folks sad.
Simplicity won, in part because of existing practice in EMACS scripting, particularly with some Asian languages.
Interesting. I maintained a couple of Emacs libraries (dictionaries and input methods) for Japanese in XEmacs, and while hyphen-separated mixtures of ASCII and Japanese are common, I don't recall ever seeing an identifier with ASCII and Japanese glommed together without a separator. It was almost always of the form "English verb - Japanese lexical component". Or do you consider that "relatively complicated"?
It might be time for the documentation to mention a specific linter/configuration that does this. It also might be reasonable to do by default in IDLE or even the interactive shell.
It would have to be easy to turn off, perhaps even provide instructions in the messages. I would guess that for code that uses it at all, it would be common. So the warnings would likely make those tools somewhere between really annoying and unusable.