Kounipo:
I thought if a line was commented out, the compiler wouldn't read any of it. I've never seen this behaviour before.
There's a sequence of things that the compiler does when it reads your input file. Interpreting end-of-line escapes is one of the first things it does. Working out what is a comment and what isn't occurs quite a bit after this.
If you haven't seen that behaviour before, it's probably because you had a blank line after the comment.