CSS Selector restrictions: why?

[bryanburgers]

Why are the CSS Selector restrictions so tight? I was under the understanding that CSS Selector Performance is largely irrelevant.

If there is a reason to restrict the CSS Selectors so tightly, can it be documented somewhere?

http://calendar.perfplanet.com/2011/css-selector-performance-has-changed-for-the-better/
http://benfrain.com/css-performance-revisited-selectors-bloat-expensive-styles/
http://www.stevesouders.com/blog/2009/03/10/performance-impact-of-css-selectors/

[cramforce]

We might relax this a bit. Need a good corpus of docs to see. It is definitely is not irrelevant. Style recalc is O(number of DOM nodes * number of rules * their complexity)

[cramforce]

Removed most restrictions