> If you want, you can serve 2.0 to newer browsers and 1.9 to older ones using our conditional comment trick

I'm really surprised they would suggest doing this. The two APIs are quite different since many functions from the 1.x branch have been removed in the 2.x or sometime behave differently (for instance `$("some <strong>bold</strong> text")` will be parsed as HTML in 1.x but considered a CSS selector in 2.x).

Basically, I really wonder what could be the benefit of using this kind of conditional comment trick.