Maybe you might want to add a bit to the duplicate detection algorithm to remove the "www." before checking if it is a dupe. I only say this because an article was submitted by two different people with exactly the same title. The only thing that differs is the "www." prefix on the url.

The two stories:

http://news.ycombinator.com/item?id=594605

http://news.ycombinator.com/item?id=594525