It wasn't a repost - the mods sometimes refresh a story to give it a second chance at more engagement. When you see the same post come back a day or two later, with the same comments, all with their timestamps updated to the current time, you can be confident this is what occurred. You can also tell by looking at the post history of OP - it shows an original posting date of 4 days ago, even though this post shows as a few hours ago. Not a bug, not someone spamming this site... this is a normal and fairly cool feature of HN.