From The New American:

… the company was awarded a patent by the U.S. Patent and Trademark Office (USPTO) earlier this month for an automated system that would “receive a list of proscribed content and block comments containing the proscribed content by reducing the distribution of those comments to other viewing users” while continuing to “display the blocked content to the commenting user such that the commenting user is not made aware that his or her comment was blocked.” A better definition of shadow banning would be hard to write.

Facebook is sure to have a good explanation of what this means, and how the company uses the automated system for the greater good… at least, the greater good according to Facebook.