VRSpace.org

SessionManager.afterConnectionClosed
calls
WorldManager.logout
which calls exit() first, and only then deletes guest users.
Exception in exit could prevent user deletion.
Candidates:
client scene update (likely)
client notify listeners (unlikely, sendMessage in try/catch block)

None of the above, most likely client errors.
There's one thing sure to keep user in the database forever - killing server with -9.
Eager load/remove/positioning of avatars implemented on client and server, this is no longer relevant.