This reminds me of a time not too long ago when I was teaching programming courses; at least one of the students would somehow manage to get one of these or other weird characters into source code, resulting in much confusion. On the bright side, I take advantage of the opportunity and an impromptu lesson in data representation and character encoding soon follows.
It's also one of the things where a hex editor is extremely useful --- even if you're not working on low-level, seeing the bits directly can be a great confirmation of correctness.
I had this happen to me once (and only once, I learned my lesson). Our professor gave us a PDF with the problem description and it had a bit of code in it we were to put into our final program. Well, when I copy and pasted it some of the spaces copied as non-ASCII space.
Oh god pasting code from a PDF, that brings me back.
Doesn't your editor handle that? I don't exactly remember but I kinda remember having a button to convert pasted characters to ascii (mostly used for those annoying stylized unicode quotes)
Apparently Atom didn't/doesn't have that feature, at least to automatically display when problematic characters are present. I believe I ended up taking a hex editor to my code to see what was wrong, since it was only a single loop that appeared to stop the compilation.
It's also one of the things where a hex editor is extremely useful --- even if you're not working on low-level, seeing the bits directly can be a great confirmation of correctness.