I'll copy a comment of dang in a similar case: https://news.ycombinator.com/item?id=11273580

> HN doesn't treat posts as dupes when a story hasn't had significant attention yet. See https://news.ycombinator.com/newsfaq.html .

> This is because we want good stories to have multiple chances at making the front page. The current story is a great example. In fact, we invited tdurden to repost it, as we sometimes do when we notice an article that we think the community might find interesting, but which fell through the cracks.

> We're working on a better duplicate handling system that will reduce the number of reposts in the story stream, but getting it right is surprisingly subtle, and we'd rather take longer than get it wrong.

Here's how I understand it, but some of this might be wrong.

Good stories sometimes get missed because there's so much posted to /newest.

The dupe detector is currently weak to allow reposts. A repost is better than missing a good story.

https://news.ycombinator.com/item?id=10223645

How did what happens? Not all times of the day are good for posting.

More people are active on HN at certain hours (mostly related to US work times, where the big majority of users come from).

And articles can both regularly either fails to catch up until some nth submission, or get on the homepage again and again every few months (even if it's the same article).