how to separate the wordpress comments with php

In wordpress there is a way to separate the comments your blog receives in two categories: trackbacks/pingbacks and actual comments.

I'm wondering if there is a way to divide the comments in more categories: for example comments from friends or comments from popular blogs, etc.

In mininova.org they have separated the comments in actual comments and thanks comments. Is there a way to do that in wordpress?

Any ideas?

 

using a specific flag for each comment.
required DB alteration and a little code change in comments.