This is putting the cart in front of the ox yet again. A few mails up Aryeh and Gregory both come to the conclusion that automatic flattening is useless. Yet category flattening would be a prerequisite to intersections. The only way to get proper intersection is manual flattening i.e. atomic categorization. As long as nobody is pushing commons _hard_ to change their categorization system _nothing_ will happen and we'll meet on this list again in about one year repeating the same discussion.