My Top Commentators is a plugin that allows a blogger to discover who are the most active commentators on his blog (via the WordPress Dashboard, so other people will not see this information). You can also use different time frames for this, so you can see the top commentators: Today, Yesterday, Last 7 days,This month, Last month, This year, Last year.

Secondly, you can also see all the comments left by a single person, and edit or delete them via the plugin interface. People that comment often on your blog are your most loyal readers, so it would be useful to know exactly who they are.

Pricing: Free
Requirements: -
Source: http://www.dailyblogtips.com/my-top-commentators-wordpress-plugin/