if I ever saw this in a project, I would remove those comments in a heartbeat. The behavior here is specific to the json parser. JavaScript is not the entirety of programming.

It does break the json parser in the Go standard library, in a totally nonobvious way: http://play.golang.org/p/BsDd47vWna

I would be surprised if it doesn't break many parsers, especially json parsers in static languages. If you want that sort of behavior, don't use json.