I use Disqus as my main commenting tool which you see at the bottom of each blog post.
It is used by thousands of blogs and has become the standard on professional blogs. It has its own community, and you receive emails and a dashboard of blogs that you have commented on as well. An all-around awesome tool.
Disqus is a global comment system that improves discussion on websites and connects conversations across the web.
Pricing: Free of charge.Social Snippet