I think it's well worth a repost.

Excellent tip though, excellent.

Maybe there should be a "most often reposted" section in HN.

I think there already is, it's just that the cache gets flushed form time to time.

What would be nice would be a way to merge several stories in a same comment thread, and maybe then "bump" older threads in case of reposts.

The simple link check exists. It's too simple and easily circumventable, though.

Even if it weren't the case you could probably find alternative sources to do a repost.