Probably the most ground-breaking feature of MOZ (as far as I know nothing like this has ever been done before), transparent multilingualism means that two different players can be in the same room, engaging in the same interactions with the MOZ, in two completely different languages.
Note that MOZ does not even attempt to translate text spoken by players. What it does do is give builders and programmers the ability to write their descriptions and verbs so that players can see the same room or run the same command in different languages.
This is a big topic, but it basically means that MOZ is more secure than you might expect, although it is secure in different ways than most MUDs.
There are a variety of papers on the 'net about capability security, but the page devoted to introducing capability security on the E language home page is probably the best place to start.