The "chat bug" is almost impossible to fix
Reason is that /l, /s etc work on a radius - whenever someone uses them, it gets the player's position and works out the location of players in the radius around them (i.e 10 metres) and then sends them the client messages or "chat lines"
The interiors work in virtual worlds. Player A and Player B have the same interior, and are in their houses, but can't see each other because they are in different worlds BUT they are in the same LOCATION! Meaning that they are still in the same radius!
Like I said, almost impossible to fix...unless it specifically checks virtual worlds as well as radius...which is a pain