Default Chair

In VRChat, there is a component called VRC Station. This is the basis for all chairs in worlds. The default setting allows a player to enter and sit in the station. At a technical level, when a player is in a station, the player's position is set to the station's position. This leads us to the first observation: Player positions are normally forced synced, but while in a station, the station does not need to be in the same location for everyone. The sitting player will still follow the station where you see it. 

The most basic version of repositioning remote players is a default chair with some additional logic to move it. As an example, you can create a simple Udon program such that when a remote player is in the chair, the station is moved -1000 below the floor. This creates a situation where the player sitting in the station is still in the same location, but for everyone else, the player has vanished. Privacy concerns aside, the player sitting in the station is no longer at the same location for everyone. 

UdonGraph

UdonSharp

CyanTrigger