This is not necessary since you usually add the CS version to your dev dependencies (package.json). That should be enough. The resulting JS should not show any reference to CS at all.
You assume coffee code running in the context of a npm-based package.
coffee can also be used in the browser using the Rails asset pipeline (where you'd have the Gemfile, granted), or other methods (where you might have no indication).
The only place where I would like this line not to be shown is when I try to sneak coffee code into a codebase where only specific languages (JS in this case) are allowed and all code has to be originally written in any of these languages.
But honestly, if you are this devious, removing the line will be easy for you and, secondly, even though the coffee compiler produces really nice JS code, one glimpse is usually enough to recognize coffee compiler output as such, so removing that one line hides nothing.
