keith you should look at implementing Disqus (www.disqus.com)
it will let readers collapse a thread (so if they are not interested in reading a particular group of comments because of some flame war going on, they can scan past it quickly). It also gives you finer moderation controls, and the ability to ‘bump’ comments down to the bottom of a thread to keep more interesting comments at the top.
The comment content here is great – there is just the odd troll. Having an ‘open’ comment policy is a good thing, as it invites people to participate. Even people who leave short/bad comments initially shouldn’t be banned or block, because they can go on to add a lot of good stuff later on.
One thing, there are interesting discussions in deeper/older blog posts which are hard to track. People usually scan comments on a post and then never go back to it – the solution here might be to have a ‘recent comments’ page, which shows all the comments from all posts sorted chronologically, with the most recent at the top (this is easy to do in wordpress, and you can also give it an RSS feed)