WordPress Plugin: Kittenâ€™s Friendly Comments
This plugin will allow you to whitelist your friends comments and moderate everyone else.
When a new comment is posted, this plugin checks to see if the authors email address has been use to submit a comment that was previously approved. If it hasn’t, it will be flagged for moderation, and you can decide what to do with it. If a comment is submitted by someone whoâ€™s been approved in the past, the comment posts as normal, with no intervention from the user or administrator.