Free advice -- worth what you paid for it: for sites who don't get many comments, it doesn't matter what they use. For those that get lots of comments, the two most important things are building a community and moderating it. To a large extent, community depends on history presented cogently. To that end, showing a user where they are in a thread and what they haven't yet read is paramount.
Build distinctly better moderation tools, and the experience will be enjoyable, too.
Build distinctly better moderation tools, and the experience will be enjoyable, too.