I`m with Bart on this topic.
It's hard enough to keep up with blogs let alone with comments on the comments you made on those blogs. And as people in your comments noted .. Trackbacks should solve this problem
I actually send a trackback to Leo which made my comment show up in his comments.
Commenting to it on my own blog and trackbacking to the original post actually gives you the benefit of not having to authenticate / register on a gazillion blogs. it gives you better visibility on the comments people make on your comment (If they are nice they include 2 trackbacks), since you don't need to track it on other blogs.
Lots of blogging tools have features to detect trackback urls from original posts that you point to , Drupal can even do that from a cronjob if you want to.
It's however the other side that also needs to have trackbacking allowed.
If the trackback system doesn't work , or if you prefer not to enable it due to the shitload of spam you get on it there's always Technorati telling you that people have been pointing back to you.
Might I suggest you take a look at the Drupal Trackback module , if you enable it this post on my blog should show up a s a comment to your blog entry and we'll all be happy :) And Technorati will update your Authority