Bernhard Kau

This plugin enables blog admins and editors to manage the notification of incoming comments. As WordPress only has the option to notify on every comment, the email account of the admin may recieve many email each day. Notification is also limited to the admin only, so only the admin user will receive an email for incoming comments.
Using the plugin you can subscribe to a RSS feed that contains even comments that has to be moderated. Every feed entry has the links to delete a comment, mark a comment as spam or approve a comment, if the comment has to be moderated. If a comment has been marked as spam, it will no longer appear in the feed.
A list of all of my plugins can be found on the <a href="http://kau-boys.de/wordpress-plugins?lang=en" title="WordPress Plugins" rel="nofollow ugc">WordPress Plugin page</a> on my blog <a href="http://kau-boys.de" rel="nofollow ugc">kau-boys.de</a>.

Kau-Boy's Comment Notification

This plugin enables blog admins and editors to manage the notification of incoming comments. It offers a special RSS feed with all comments, including …

denishua

When a reply is made to a comment the user has left on the blog, an e-mail shall be sent to the user to notify him of the reply. This will allow the users to follow up the comment and expand the conversation if desired. 
Detail information: http://theme10.com/comment-reply-notification/
中文介绍： http://fairyfish.net/2008/11/03/comment-reply-notification/

Comment Reply Notification

When a reply is made to a comment the user has left on the blog, an e-mail shall be sent to the user to notify him of the reply.

Kau-Boy's Comment Notification vs Comment Reply Notification