The dupe detector needs to be improved so that submissions cannot be posted twice. It works when I try to submit something which just has been posted the same d

The dupe detector needs to be improved so that submissions cannot be posted twice. It works when I try to submit something which just has been posted the same day, but there must be some logic that allows it to be reposted and also the URL check isn't sufficient. Alternatively a merge of posts by moderators would be okay, too.