How to become a shadow player

The game will not render your player model if it starts with the character "ą".

Steps

Invisible player with nametag

The console will print out [/???.???.???.???:?????] LOG IN FROM UNKNOWN CLIENT when you log in.

Open MultiMC
Select preview 2, and click on Launch Offline
Enter the name ą<any character>
Launch the game

Visible player without nametag

Nothing will happen.

Open MultiMC
Select preview 2, and click on Launch Offline
Enter the name ś<any character>
Launch the game