Via the American Political Science Review, Harvard researchers pinpoint the surprising heart of authoritarian state censorship — anti-government criticism is in fact allowed, but not references to collective action of any sort:
We have devised a system to locate, download, and analyze the content of millions of posts from nearly 1,400 different social media services all over China before the Chinese government is able to ﬁnd, evaluate, and censor (i.e., remove from the Internet) the subset they deem objectionable. We compare posts censored to those not censored.
Contrary to previous understandings, posts with negative, even vitriolic, criticism of the state, its leaders, and its policies are not likely to be censored. Instead the censorship program is aimed at curtailing collective action by silencing comments that represent, reinforce, or spur social mobilization, regardless of content. Censorship is oriented toward attempting to forestall collective activities that are occurring now or may occur in the future—and, as such, seem to clearly expose government intent.