It's a great point that there aren't any obvious examples in the US of large heterogenous groups with good comments. That said I also am not aware of any attempt to do even Slashdot-like crowdsourced voting (including explanation of reasons for voting, meta-moderation) at scale, or to take the next step and provide a richer user experience to make it easy for users to be able to filter out what they don't want do see.