On HN, a small number of reposts is ok if a post hasn't had significant attention yet in the last year or so. This is in the FAQ: https://news.ycombinator.com/newsfaq.html.

It's true that repostiness per se is annoying, but it's more annoying for good submissions to miss out on attention because /newest is something of a lottery. Allowing a small number of reposts is a way to mitigate that randomness, until we can maybe work out a better solution.