Anyone using a monospacdd font, a font where underscores are separated, or a run-together proportional font that they are even a little bit familiar with, because of the relative width of underscores and other characters.

Which, between them, covers approximately everyone.

I mean, maybe you should use a font that doesn't make it hard to figure that out. Next you're gonna say we should ban 0s and Os, Is and ls, because your font doesn't allow you to figure out which one it is.