Asaf Cohen

Now you don’t have to login to your user every time you get comment notification, you can approve/trash the comment with just one click. 
Allows authors and moderators to change comment status directly from the email notification.

One Click Comments

Allows authors and moderators to change comment status directly from the email notification.

Martin Lormes

If a comment is held for moderation an email message is sent to the comment author with a link to verify the comment author’s email address. When the comment author clicks on that link the comment gets approved immediately. This makes discussions more lively as users don’t have to wait for the blog admin to approve the comment.
Blog owners may also choose to hold the comments in the moderation queue even after successful verification. The verification status is shown in the comment lists in the admin.
If an author has a previously approved comment and his comments gets approved automatically according to the ‘comment_whitelist’ option in WordPress no email is sent.
If a comment is classified as spam by Akismet or another anti-spam plugin no email is sent.
This plugin uses the <code>commentmeta</code> table and thus requires WordPress 2.9
PHP5 strongly recommended

Comment E-Mail Verification

Wish it supported embedded html in the verification email. One note. You must have Settings -> Discussion -> Comment must be manually approved checked in order for it to work. Once I figured that out, it works just fine.

Still works

If a comment is held for moderation an email message is sent to the comment author with a link to verify the comment author's email address.

One Click Comments vs Comment E-Mail Verification