O RLY Comment Spam Search creates a quick link to make sure comments aren't spam.
Remove trackbacks from your sitewide and individual post comment feeds, and/or have alternate feeds for comments or trackbacks only.
Uses wp_cron to delete comments each day that are marked "spam" in the database.
Enable moderation requests and notifications by email to all administrators.
Display commenters' OS and browser infomation next to commenter link.
Riffly is a free service that easily plugs into your site allowing visitors to
create video/audio comments.
This plugin protects your registration, login and comment forms against spambots with a simple math question.
Send a notification on comment to the author of the post
Says Something Else replaces the default “SoAndSo says:” in WordPress comment threads with whatever you specify.
Publish all your comments directly to a twitter account. You can customize the message published.
Disemvowel comments lets you selectively remove vowels from user comments, if you think they are trolls.
Add retaggr.com functionality to your blog - image tagging of any image,and totally customizable Profile Cards.Demo and help at http://www.retaggr.com
This plugin allows a user to sign in using his/her Friend Connect account.
This plugin shows the total number of articles and comments as well as statistics about which platforms and browsers were used in comment writing. It
Allows for the use of a template tag which returns a comment (specified by its ID) for use as an object.
RSS link for this tag.