Some Facebook users found the following message when trying to post a comment on Facebook. Apparently, Facebook blocked the comment calling it "irrelevant or inappropriate."
It is not a secret that Facebook monitors your comments to block spam or offensive content. Users can flag inappropriate images, comments and videos for Facebook to remove. If a user is flagged too many times, they are no longer allowed to post on the site. It also blocks friend requests from being sent if it looks like spam, because the 2 users don't have many friends in common. There have also been reports of people being temporarily blocked from posting on the site entirely after writing too many comments within a short time period.
However, this error message sounded as if Facebook was analyzing the contents of the message and deciding whether it was relevant or not, which would go beyond traditional anti-spam measures and veer into censorship territory.