I'd add that the publisher should have a syndication option for the comments. In other words, the publisher should get a non-exclusive, free right to syndicate all the comments along with the original blog post. A conversation and the corresponding blog post should always be able to go hand in hand.
Yet this is part of the conversation about that post but it's happening outside the blog. People will discuss a blog post wherever they want, and every conversation will be different. I'd rather discuss a Techcrunch post here than on Techcrunch, for example.
