It's definitely a cool article, I don't mind seeing it twice. I love the idea of having these tools with postgres and not having to use thinking sphinx or solr right as quickly.
I think you can repost about a year. It could have changed tough.
I don't know when it was posted, but it definitely was less than one year ago. My main data point is that it still is living in an open tab in Chrome. I have a couple of sites which allow submitting links. I know people can get around my requirement that they are unique pretty easily. I'm sure HN is more sophisticated but I think that just having different url parameters might qualify as a different link? Sometimes a url parameter change really does point to a different page, so it might not be possible to eliminate duplicates that have the same url with just different params.
URL parameters don't qualify as a different link (or else anyone submitting a url without removing them would have unique posts). I always thought the rule had to do with comments being allowed on the post, which, I believe, are based on comment activity. My assumption was as long as an article still allows comments, resubmissions don't become new posts.
I don't know why and I can't help you, in both case I didn't post it. But we don't have multiple url for our blog.
I find it odd to be honest as the post was posted on HN the 29th of September (base on Google Analytic)