I don't know if you've used a lot of blogs/CMSes/etc, but you definitely overrate their commenting systems. Most of them are crap. That's why Disqus is so popular, because it has tons of cool features (like the little popup that says when someone has posted before you).

Heck, Disqus is better than 90% of the forums out there (Hi, there, PHPBB or vBulletin!).