Earlier quoted context omitted.
As others have said, you can always strip comments in production builds. But I agree that this is utterly silly - I'd like to see a movement to deprecate including comments in parsing at all. Anything that makes use of such a feature is hacky weirdness from the start.
Function.prototype.toString() should be deprecated anyway. There are very few to no legitimate uses of it that are any better than awful eval() hacks. Re: this comment, if you just don't make huge comments inside the body, but rather above it - as is the usual standard - this is less of an issue.
The toString() on a function is very useful in more ways than awful eval hacks. The most useful way is how I use it in msngr.js for creating keys for methods that handle events.
So let's say your custom object has a way to handle events. Surely you want to allow more than one method to be hit for each event, right? So internally to your object you keep track of this by the method's contents as a sort of key or hash that always points to that specific method. Then you can remove handlers by simply passing in a method. No requiring special keys or anything to identify a function as a function is its own key.
Make sense? It's most useful for developers who work on frameworks or objects that require some custom eventing that can be used by multiple places.
If you really want to deprecate this functionality then you need to provide a way to hash to create a unique key based on a function itself. The only other way around it is adding more verboseness to the language or event handler calls which doesn't add anymore clarity.