It does seem like a bug, especially given that this didn't happen in the past. At one time, if you resubmitted a URL that close together, the second submission

It does seem like a bug, especially given that this didn't happen in the past. At one time, if you resubmitted a URL that close together, the second submission was just automatically translated into an upvote on the first one. If they changed it intentionally, I'd be really curious about the reasoning behind that. Not sure if anybody on the HN crew will be willing to comment on this or not though.