Communications Major

Internal documents suggest Facebook has long known its algorithms and recommendation systems push some users to extremes.

Twitter and Facebook on Wednesday locked the accounts of President Trump, which prevents him from posting messages to his more than 88 million followers on Twitter and 35 million followers on Facebook, after he published a string of inaccurate and inflammatory messages on a day of violence in the nation’s capital.

The moves were an unprecedented rebuke of Mr. Trump by the social media companies, which have long been megaphones for the president.