Just a suggestion -- have the submission routine search for prior appearances of the offering, especially effective when the URLs are identical. Then diplomatically suggest that the submission might make the submitter look like a craven copycat. :)
HN's dupe detection has always been an honor system. We leave it so porous because we want to give the best stories multiple cracks at the bat. Otherwise randomness and churn, especially during peak hours, would bury far too many. Of course, this also makes the dupe detector easy to game, so we ask people not to game it. A small number of reposts is ok.
Several users have complained that randomness and churn are still causing many good stories to disappear without a trace. After looking at the data, we agree, and we're working on some experimental solutions for it.
If there's one driving idea behind HN, it's optimizing for curiosity, which cares about quality over quantity, so losing any of the best stories is a big (bad) deal.
I wrote the blog post but this one and the one you linked to weren't submitted by me nor do I know who they are. I only found out via an analytics spike and asking someone who emailed me some VPL additions that it was submitted again.
Submitters: please check whether an article has been posted before. In this case, running the title through HN Search returns the above immediately.
Once a story has had significant attention on HN, we generally don't allow reposts for about a year.