Subscribe to Double-Opt-In Comments

Allows readers to receive notifications of new comments that are posted to an entry, after they successfully used the mandatory double-opt-in process to verify their e-mail address.
First, the user will get an e-mail with a confirmation link, after the user has confirmed the subscription, he or she will be noticed about new comments. This reduces junk and other unwanted e-mail communication.
This plugin is based on Mark Jaquith´s “Subscribe to Comments” plugin. More information on my blog: sjmp.de.