Commands affecting the game status should be executed server side, but they act weird instead, and I can't really understand where they are executed.

Example: the /bw-st v 10 command should change the player on the server, then send a PlayerTransformationChangedMessage to the client player to actually make it a lvl10 vampire. This never happens, because the message only gets sent if world.isRemote() returns false, but inside a command this returns true, and the player is left out of sync (Vampire on the client, with no visible bar buttons, not a vampire on the server. Relogging without closing the client window shows bar button on login because of data that should be reset on logout. It's kinda confusing).