I'm not so sure about that because CoffeeScript is a very fast moving language (one of its benefits) and it doesn't make sense to slow down the iteration cycle by integrating it with browsers directly. Then you would have to worry about which CoffeeScript features you could take advantage of, instead of just compiling to the lowest common denominator of JS, so to speak.

(This is exactly the reason Brendan Eich has said he prefers the "compile to JS" approach to incorporating other languages of a VM into browsers.)

Should read or a VM -- I still don't entirely understand how HN determines when you can still edit a post, pretty sure I've edited posts this old before.

CoffeeScript needs to be a fast moving language because it's still being developed. I imagine that, like most languages, it will eventually settle into a fairly stable, mature language spec.