It works in practice though, because there’s no CSS syntax that uses //, so you can basically turn off any line that way by causing a syntax error. CSS fault tolerance makes it just ignore the line. Not sure if it’s wise to do this, but it works.

That’s a valid point. I’ve never actually tried it, because my editor always tells that it’s wrong. I suppose I could edit raw CSS with my editor in SCSS mode and just be careful to not use any incompatible features. :)