So, where exactly would you like to put AJAX support and why would it be better to what there already is? When you have that straight, we can agree or (most likely) disagree with your proposals.
I don't know about the OP, but three places where it would be apparent to me are the chatterbox, voting, and moderation. I've always thought it odd (and probably expensive) that all three actions required a full refresh of the page to do what amounts to a tiny change in the output.
The only easy day was yesterday