Boost your Craft site by allowing users to post comments:

• Add user comments to any type of element, such as users and content items
• Get a nice overview of submitted comments in the CP
• Moderation: delete, approve or mark as spam in the CP
• Moderation: modify comment contents in the CP
• Comment forms are signed so malicious users cannot submit comments to arbitrary content

More info on the plugin's documentation site: http://io.24hoursmedia.com/comments-work