[DrScump]

A key aid would be a disincentive to posting duplicates, e.g. lose rather than gain karma points by doing so.

Many sites are trolling for extra hits by deliberately munging their URLs, either appending random crap to the URL itself (e.g. gamedevdaily.io) or appending fake fragment identifiers (medium, signalvnoise) to evade automatic dupe detection using simple URL duplication.

In the meantime, dupes are "winners" for both the poster (intercepting activity and, thereby, points) and the site (gaining more visibility, since your site appears 2X-4X more in HN than it would otherwise).