HN's dupe detector only treats a repost as a dupe in these two cases: (1) the earlier post is less than 8 hours old; or
(2) the earlier post received significant attention.
In this case crecker's submission (sadly) didn't receive much attention, and other submission showed up more than 8 hours after it, so the dupe detector let it through. This is in the FAQ: https://news.ycombinator.com/newsfaq.html.
It sucks when a submission doesn't get traction and then a later copy of it does. But it would suck worse if a story like this only had one crack at the bat—many good stories would go unnoticed if we did it that way. That's why the dupe detector is left porous like this.
We're eventually going to implement a karma- and credit-sharing system for cases like this. In the meantime, I always tell people that it evens out in the long run as long as they keep submitting good stories—that's the nature of randomness.
