No they don't, that headline is very misleading and is a huge misinterpretation of the paper. For a small portion of the userbase, Facebook detect IF they self-

No they don't, that headline is very misleading and is a huge misinterpretation of the paper. For a small portion of the userbase, Facebook detect IF they self-censor and just transmit that. They only see metadata, and not the actual contents of the message.