What if someone wants to re-post something that was posted 1+ year ago to see new opinions? I think at the moment it navigates back to old post without creating a new one.
HN's duplicate detector is left weak on purpose so that people can repost interesting things, either because they haven't received significant attention or because more than a year has passed. You may need to change the URL slightly for the repost to work.
Because it's an honor system, we ask people not to abuse this. Examples of abuse are deleting posts that didn't get traction and resubmitting them; or reposts of the same material over and over. In general, we're more tolerant when people are reposting things because they're interesting and less tolerant when they're promoting something.
Submitters: please don't post stories that just point to something else. Post the something else instead.