I think what I’d prefer to do is make a bookmarklet that you can click when you’re on a blog post page, which then passes the URL of that posts rss file to a web app which subscribes you to that RSS feed and notifies you via Jabber when it updates.
In order for this to be useful this means that you’d need to provide single-page posts (like Sam Ruby does, although his is the only weblog I can think of off the top of my head that actually does this, I have no idea if you can do this in MT, but Mark Pilgrim doesn’t, and he normally does everything 😉 ).
This would be extremely useful for seeing when a post you’ve commented on, or find interesting has been updated.
obviously if you have an rss feed for your comments you can subscribe to it anyway, but who wants to clog up their aggregators with stuff like that? and this would be more immediate anyway. and i’ve stopped using my aggregator. 🙂