Disqus is the world’s favorite discussion platform. It has awesome features and powerful tools. Use it now to engage your audience, increase activity and discover your community.

Key features:

Threaded comments and replies
Notifications and reply by email
Subscribe and RSS options
Aggregated comments and social mentions
Powerful moderation and admin tools
Full spam filtering, blacklists and whitelists
Support for Disqus community widgets
Connected with a large discussion community
Increased exposure and readership

Demo and Help here: http://www.oc-extensions.com/Disqus