Comment Log (or clog) is a plugin that allows you to store a copy of a comment you make on another site. 
This is done through implementing the <a href="http://peopletab.com/restta.html" rel="nofollow ugc">RESTTA</a>-based cLog API. 
As long as the remote site supports the API, you can keep track of any comments you make. 
This plugin also allows those that comment on your blog to keep track of their comments. 
The full details about the cLog spec can be found <a href="http://peopletab.com/cLog.html" rel="nofollow ugc">HERE</a>
<h3>Version Log</h3>
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1.2 : Fixed a major bug, it should actually work properly now for the handful of people that use it 😀
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1.1 : Minor updates, you can select the page to display the comment log on from a dropdown now, and confirmed it working with 2.5
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1.0 : Initial version.
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Comment Log

Keep track of your comments on other sites using the cLog API.

Mark Jaquith

Joen Asmussen

Subscribe to Comments is a robust plugin that enables commenters to sign up for e-mail notification of subsequent entries. The plugin includes a full-featured subscription manager that your commenters can use to unsubscribe to certain posts, block all notifications, or even change their notification e-mail address!

Subscribe to Comments

Subscribe to Comments allows commenters on an entry to subscribe to e-mail notifications for subsequent comments.

Comment Log vs Subscribe to Comments