If the link was the same, shouldn't you get a warning that this was already submitted? If I submit something that has already been submitted, HN automatically give a point to the previous submission.

Which is the way I expect it to work to avoid double submission and parallel discussions. The thing is: I have not quite understood why sometimes it works and others not.

Submitting an identical link starts working after a few days since the previous submission.

Is there a technical reason for this?