Elizabeth Dwoskin:

Lyons said she soon realized that many people were reporting posts as false simply because they did not agree with the content. Because Facebook forwards posts that are marked as false to third-party fact-checkers, she said it was important to build systems to assess whether the posts were likely to be false to make efficient use of fact-checkers’ time. That led her team to develop ways to assess whether the people who were flagging posts as false were themselves trustworthy.
 “One of the signals we use is how people interact with articles,” Lyons said in a follow-up email. “For example, if someone previously gave us feedback that an article was false and the article was confirmed false by a fact-checker, then we might weight that person’s future false-news feedback more than someone who indiscriminately provides false-news feedback on lots of articles, including ones that end up being rated as true.”