Anonymity And Immersion

In most games players can be identified by name, which is always displayed above character. Another system is making such names invisible, unless the character(not the account) adds player as a friend(or entirely absent: characters only choosing the color of their text in chat).
In this system, players are only shapes and appearance, without identifiers:
without a distinction between NPC and players, various roleplay scenarios can be created on the spot, making the game immersive and filled with player-generated content. Changing character appearance would effectively erase previous past or change it role, without switching to another character.