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Highlight comments with a background color in the WordPress Comments Admin pages. Choose the criteria for highlighting a comment, add a note to show it with, and pick the highlight color.
This plugin is “for internal use” and only highlights comments within the WordPress Comments admin. The typical use case for this plugin is to inform/remind users about what to do for a particular type of comment. Examples:
<ul>
<li>
Comments from John Doe – Always approve unless it’s about topic XYZ
</li>
<li>
Comments from IP 12.34.56.78 – Give a personal, non-standard response to these comments
</li>
</ul>
You can highlight a comment based on the contents of the commentor’s name, email, or IP address.

Comment Moderation Highlights

Highlight comments in the Comments Admin. Pick a color, add a note.

Speedboxer

The Comment Approval Notification plugin will send an email to the comment author when you approve their comment. The email sent is fully customizable, with shortcodes, through a settings page.
Please note that this plugin has only been tested with PHP 5.2.x.
A full list of available shortcodes is available <a href="http://mattsblog.ca/plugins/comment-approval-notification/#shortcodes" title="Available Shortcodes" rel="nofollow ugc">here</a>.

Comment Approval Notification

Sends an email to the comment author when their comment gets approved (only if it's held for moderation).

Comment Moderation Highlights vs Comment Approval Notification