In src/effects.js in current jQuery 2.0.0pre in lines 443-452 there is code:

// Remove in 2.0 - this supports IE8's panic based approach
// to setting things on disconnected nodes

Tween.propHooks.scrollTop = Tween.propHooks.scrollLeft = {
	set: function( tween ) {
		if ( tween.elem.nodeType && tween.elem.parentNode ) {
			tween.elem[ tween.prop ] = tween.now;
		}
	}
};

I guess it should either be removed or the comment should be changed if it's still needed in 2.0.x.