Posts with >5 upvotes tend to go to the front page for at least a few minutes. More than that many people tried to repost it.

What was the post? I'd be curious to look into it, if you don't mind saying. (Edit: might be best to email [email protected].)

It was https://news.ycombinator.com/item?id=9856637

Ok, there was another factor. When a site is the source of many stories marked lightweight, it eventually gets penalized as a lightweight site. We have software that does this, plus moderators do it.

This was the case here: that site has been the source of, not spam exactly (which is why it isn't banned), but a lot of unsubstantive and/or derivative articles. The post you submitted is an example of the latter, since it was derived from a Reddit thread.

The penalties I'm talking about don't make it impossible for a story to get traction, but they do set the bar higher. So you were right that it was randomness, but the randomness was also skewed.

If people try to submit an already posted URL their submission is blocked and they are redirected to the original URL which gets an upvote. So if you see a flurry of upvotes on one of your old submissions it's possibly because people have started trying to post the URL.

I think thT's how it works.