The metrics they use for exercising editorial control do not matter for this line of logic. The fact that they are exercising editorial control, promoting some

The metrics they use for exercising editorial control do not matter for this line of logic. The fact that they are exercising editorial control, promoting some posts, censoring others, rather than neutrally carrying the content people wish to send (like a phone company or an ISP) makes them a publisher. The alternative is to allow these companies to hide behind "but we didn't do it, the algorithm did". The algorithm is an agent of the company and they are responsible for its behavior like any other employee.