comments are in most languages, so I can see that angle, but you still have to be able to parse all supported languages, no small feat

you can alternatively split generated code from human written code with files, keep the mapping in something more structured like a config file

I just normally see a better way to do the same thing a magic comment does, generally speaking. There is typically a better language construct if you limit yourself to that language (most common), and config files offer much more structure with existing tooling (mostly decode in your preferred language)