[coldtea]

Exactly. And also: a UI could be badly designed even if its users don't misuse it.

Just because users might be extra careful in their use of a UI, doesn't mean the UI is not badly designed itself.

A big red button that says "Click me for free lemonade" but instead burns the whole computer is bad design -- even if the users have read the manual, so they know what it does and don't press it.