Movable Type's current combination of blacklisting, link counting, and word filtering does a pretty decent job at categorizing user comments into three categories: Approved, Moderated, and Junked. I currently have "Approved" comments (i.e., those that don't raise the filtering rules' suspicion) to appear immediately, while "Moderated" comments require my approval before appearing.
So, feel free to leave a comment. At worst, your comment may languish a bit until I approve it. :-)
This is an example of a successfully posted comment.