The reason he didn't use a private message was that his target for communication was not a player but an NPC—Dalaran Speaker, Antonidas.
There was only one message Mo Fei was sending.
Aidandenong (Ancient Dragon King): "Master Antonidas, be prepared, we can start our plan now."
Antonidas (Dalaran Speaker): "I have received your message; I hope your plan will be successful."
Mo Fei descended from the sky, but transformed into a human form.
Aidan (Duke of Altland): "You're right, the power of the Lich King is indeed difficult to confront, but there is one who can, Varian—I know you're still there, look around, how many warriors of the Alliance have been sacrificed because of you, all this chaos is caused by you, how long will you hide, my second brother, you are not a coward, you once swore to protect your people, are you going to give up now—answer me!"
Gul'dan's face twisted, and the evil fire in his eyes gradually faded.
Varian (Lich King): "I... I can't defeat him... I..."
