VSCode will add a yellow box around the character and tell you it's an uncommon glyph.

https://code.visualstudio.com/updates/v1_63#_unicode-highlighting

To note, this came about because it could be valid code and it's a security risk from copy/pasting malicious code. See:

https://certitude.consulting/blog/en/invisible-backdoor/

Just tested in the console, it gives an illegal character error and gives you the line number.

It would work for someone just starting and not knowing good tooling yet. However, the compiler should also tell you where to look and give you the area to look at as well. It'll be less clear than an IDE, though.

Yeah, doing something similar with brackets would be much more effective since that usually doesn't give a line number. Is there a unicode clone of )?

Yup. It's as if we're assuming this friend is coding inside Notepad.