On HN we don't count a post as a dupe if it didn't get significant attention. (This is in the FAQ: https://news.ycombinator.com/newsfaq.html.) The dupe detector is left porous to allow good submissions to have multiple chances. It's one way to mitigate the randomness of /newest.
Of course this also allows bad submissions to have multiple chances, but it's more important to facilitate the good than punish the bad.
Of course this also allows bad submissions to have multiple chances, but it's more important to facilitate the good than punish the bad.