This was posted yesterday and I believe it was 're-upped' by HN admins which happens occasionally to posts that I assume they believe would receive more attention if posted at another time. I did not notice the comments at the time and so cannot confirm or deny your theory about the comments. I had assumed that comments to 're-upped' posts (my term, probably not correct) did not accompany the post, but I may be wrong.
Ah, if I access these comments from the comments pages of the users who posted them, the "3 hours ago" timestamp becomes "1 day ago", so that seems to resolve things. Thanks!