I agree. I think merging threads would be the best option. I don't see every story that goes through HN, but I have often seen people post that a similar artic

I agree. I think merging threads would be the best option. I don't see every story that goes through HN, but I have often seen people post that a similar article was already posted with a link to that article. A merge mechanism (for those over a certain karma level) would allow people to recommend that two separate posts are merged into a single posting, with the karma from both added together and the responses sorted as they are now by karma.