RSS duplicate detection

As explained this problem is not simple :
http://www.xn--8ws00zhy3a.com/blog/2006/08/rss-dup-detection

So how does the Feed API module deal with this problem ?

A most common issue with RSS Item duplication is when the owner of a feed update the title of an item, most often for spelling correction, then the url of the feed is also also automatically updated on lot of web sites.

If you simply want to display a RSS feed on your home page and want to be sure that there will not be duplicate items inside his block, then maybe the best solution is to not store RSS items at all ! Instead you just cache your entire block.

You have to make a choice : if you want to use nodes for RSS items (and all the great functionnalities that came with nodes like comments, votes...), then it seems that you should accept to have a risk of duplication.