commenting – The unofficial WordPress Plugin Directory

Jetpack Follow Link for P2

Easily subscribe to a P2 comment thread without commenting using a "Follow" action link like WordPress.com has

Use the Sided plugin to create and insert discussion polls into your content.

AJAX Report Comments is a simple yet powerful add-on for any WordPress blog, particularly larger blogs with a higher volume of user comments.

The Google+ Comments WordPress plugin makes it easier for you to setup, administer and customise Google+ comments from your WordPress site.

Allows users to opt into receiving a notification email whenever a comment is made to the site.

Universal commenting system with cross-site profiles, reputation scores, and real-time analytics.

Customize and optimize comments in WordPress