HN, Slashdot and Reddit frequently have thousands of posts on a single story and many of the posts are excellent. The keys are that all three sites are dedicat

HN, Slashdot and Reddit frequently have thousands of posts on a single story and many of the posts are excellent. The keys are that all three sites are dedicated to discussion: that's practically all they do (plus story aggregation). So they are optimised for it. A simple example of how they differ from most newspaper comment sections: threaded replies. Posts that span the page width. Karma tracking.