One of the new features with WordPress 2.7 is that you can have threaded comments that are up to 10 levels deep. The problem is to get them pretty.

Here are a couple of links to get you started:

• Stylizing Threaded/Nested Comments in Wordpress 2.7
• WordPress 2.7 Comments Enhancements
• WordPress 2.7 Comment Threading
• Wordpress 2.7 Comment Style Starter #1
• Wordpress 2.7 Comment Style Starter #2