Modes for Comment Threading For High Interaction Sites

What are the ways to organize comments on sites that have lots of comments, and threaded comments, and intense debate? How do you deal with the volume of comments?

For some work on the Economist we reviewed a couple of current formats that feel cutting edge to us - after all, if you're the online host of the "severe contest" you'd better have a good way of presenting some of the viewpoints in the contest.

Gawker - Preview, but hide the replies

Gawker has threaded comments and hides the replies inside of a little info bubble. The bubble has a +/- toggle that lets you dive into each thread. The bubble shows the number of replies inside of it and gives you the names of some of the people who participate in the thread. It would be great if it could show names of people based on karma, or my friends or some other relevancy rank.

Slashdot - Tag and Vote on comments, Hide

Slashdot.org has been doing comments and online reputation longer than almost anyone else. They have a system of karma and users above a certain karma get to vote on comments and categorize them as "Insightful," "Funny" or other descriptive terms. They then hide comments below a certain threshold by default and let visitors see comments below a threshold if they want.

Digg - Vote on comments, Alternate layouts

Digg also has voting on comments and then will hide comments with a low ranking by default. It then can show comments threaded, by oldest/newest, by most popular or most controversial. In the default threaded view Digg also will show "6 replies, best has 18 diggs" to give you an indication of the level of quality of the conversation inside of a thread.