It's important to understand that this submission doesn't count as a dupe by HN's standards. On HN, reposts are fine after a year or so, and/or if an article hasn't had significant attention before (the latter isn't the case here, but often is). https://news.ycombinator.com/newsfaq.html

People post links to past discussions are not because they're bad (look at all those reposts!) but because they're good (wow, interesting comments from the past!) - at least in the best case.

Because there's so much randomness in what gets noticed on /newest, overzealous dupe detection would prevent many good articles from ever getting discussed. That would be a poor trade for better deduplication! HN's dupe detector is therefore left porous on purpose (https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...), so good stories get multiple chances to get attention. We will probably implement karma sharing amongst the various submitters of an article, though, at least when it's a first-time discussion.