[nucleardog]

I tried to find any of the original text so I could try in my editor, but couldn't so I can't say for sure but... At least copying and pasting a bunch of unicode private use characters and stuff, they're not only rendered (box with an X through it) but highlighted in bright red.

Presumably opening this file I'd see some suspicious looking code and a giant bright red block in the middle of it.

I have the benefit that I'm only working in English so "flag anything that's not basic ASCII" is workable. I could see how this could get a bit messy when you _are_ working with other languages and need to differentiate the compound characters and invisible characters and things that _are_ part of your normal use versus these that aren't.