My comment was prompted by the trend for at least one HNer to promote CoffeeScript in comments on an article related (however tangentially) to JavaScript.
I'm not a big fan of leaky abstractions, and right now that's what CoffeeScript is. It will be somewhat less leaky once this has been resolved:
https://bugzilla.mozilla.org/show_bug.cgi?id=618650
…for all browsers.
I'm happy for CoffeeScript to exist, to be able to play with it, and to see its syntax inform the work on JS.next. It has a way to go before I'd be happy to use it in a production environment.
Also, the issue is being fixed for Chrome/Firefox, which is good enough for dev work.