HN doesn't even do a consistent equality-based dupe check of the submitted URL! Submitted URLs are only checked against the URLs of past stories that are cache

HN doesn't even do a consistent equality-based dupe check of the submitted URL! Submitted URLs are only checked against the URLs of past stories that are cached in memory, and the Arc process crashes regularly, which invalidates all comment forms and starts the cache fresh again. The result is that the duplicate check is only processed against stories that have been displayed in some form in a response since the last crash. That end result is actually kind of elegant — you can only submit a direct dupe if nobody cares about the old one, but the means to that end is pretty fucked up. A worthwhile accident.