[jashkenas]

The most important thing it does is tell you which version of CoffeeScript was used to generate the file. Inevitably, as more and more coffee-generated-JavaScript begins to wind up in more places, we don't want to end up in a situation where you have to use trial and error, or distant memory, to figure out which version to use to rebuild the JS.

[Andi]

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.

[pilif]

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.

[lukeholder]

This is now automatically inserted into the top of the generated javascript as of coffeescript 1.3