Every few days I submit one that doesn’t get a lot of traction but I come back in 2-3 days and it is on the home page, I think these are responsible for maybe 1/3 of my karma but well under 5% of actual submissions. I dunno if these got resubmitted but still attributed to me or if it is part of dang’s “a good submission got missed” program.

My guess is that those links are added to the second chance pool. https://news.ycombinator.com/pool

But the ways of the HN are deep and mysterious, so that's just a guess.

This is the best guide I've found: https://github.com/minimaxir/hacker-news-undocumented