Electronic Frontier Foundation has published a booklet online in PDF format, “Censorship in Context: Insights from Crowdsourced Data on Social Media Censorship”, link here. The authors are Jessica Anderson, Kim Carlson, Matthew Stender, Sarah Myers West, and Jullian C. York.
The report shows that pre-emptive censorship by social media companies has been common throughout 2016. “Milo” was banned from Twitter soon than I had thought (and “Real Strategy” has just been banned).
One concern is to make content moderation more transparent, especially if content is taken down because of user report or some other scheme.
There are fine distinctions, between criticizing and country, and criticizing the people of a religion or ethnic group. Donald Trump had a lot of trouble with this, to be sure.
The report does consider the "fake news" problem that the 2016 Election amplified.