Hm. I think the kind of fake news most people are worried about on social media has properties which distinguish it from merely "factually incorrect information

Hm. I think the kind of fake news most people are worried about on social media has properties which distinguish it from merely "factually incorrect information". It's a kind of "supernormal stimulus" - high virality, engineered to trigger tribalism and strong emotions in susceptible recipients. The properties which make it a "weapon" are the ones which you'd want to mitigate. Unfortunately those properties also happen to goose the engagement metrics of social media companies. Source reputation, rate and pattern of viral spread should be taken into account, as well as content itself and user flags. Also user engagement behaviour - e.g. average user shared this after reading for less than 10 seconds. Basically, highly partisan content spread quickly by unthinking users, from a low reputation source. Unfortunately the networks themselves have the best metadata to work this stuff out... and the least genuine desire to do so. I'm in the "solving the worst of this looks fairly tractable" camp, but I agree that bare source text is going to be hard to work with.