Reposts are fine if a story hasn't had significant attention yet: https://news.ycombinator.com/newsfaq.html. On HN we try to give good stories multiple cracks at the bat.
Eventually we want to implement a karma-sharing system so earlier submissions benefit from reposts that catch on. In the meantime, it's a bit of a lottery—but if you submit enough good stories it evens out over time.
on edit: but I guess it's been a while.