It is pain to reply to follow up comments on blogs and various site. We maintain a site ggsipu.info which has more than 10k members and people ask so many questions via comments but they have to come to the website to post the comments. Which is pain!!
Drupal has a module to save time and make it very easy for the site visitors to reply to the comments right from their mailbox.
MailComment does just that. It is a gateway module for responding to posts via email. It links outgoing notifications emails with incoming email responses using a combination of mail parameters and digital signatures.
When enabled, it adds to outgoing notifications emails a message that looks like:
((( Reply ABOVE this LINE to POST a COMMENT )))
Then the receiver just needs to reply to the mail and the text above will be posted to the original thread as a comment.
Read more on the Module Page: http://drupal.org/project/mailcomment
and yes Drupal Rocks!!!!