I think there's a unique URL filter on submissions; but not a unique story filter on submissions (which would be a rather difficult AI problem).
Even with different URLs, there's really no need for 10 different stories about the MacBook Air to be posted here -- it would be much better to have one Hacker News item and have URLs to other articles posted in comments.
Even with different URLs, there's really no need for 10 different stories about the MacBook Air to be posted here -- it would be much better to have one Hacker News item and have URLs to other articles posted in comments.