They'll get a warning and if they refuse to stop we terminate their account. It is reasonable to defend territory. However, it would be RPK to just attack without first speaking with the trespasser. If the trespasser refuses to leave, an attack is one acceptable option. We have a very broad definition of roleplaying.
All rooms lead to the one City of Dreams.
Right now everyone is in a single world. We'll keep everyone in the same world as long as there is room for them. At the moment there are occasionally overcrowded areas, but plenty of space. The Internet is filled with latency, hiccups, lost information, and downright outages. It's a reality.