When a user is removed are all of that user's questions and answers, and all answers to the user's questions, also removed?
It depends. There are two forms of removal:
- Deletion deletes all posts with a negative vote total. On posts with a non-negative vote total, it denormalizes identity (as in LVK's comment).
- Destruction deletes all content, but it is only usable on users with less than 500 reputation. This is reserved for spammers, etc.