Improvements to user deletion

[tomdxw]

User deletion in WordPress, at the moment, is not straightforward.

When you click "delete" on users who have authored content, you are presented with this ultimatum:

At my company, we build and host WP sites for clients and we almost never make decisions about content. But we do sometimes want to delete users, for instance in the situation where a person who works for a client leaves their position as they have been promoted or left for another job. In that case we would like to be able to delete the user account of that person. But without knowing how to answer the question of which user to assign their content to, we're forced to ask the client to make that decision.

With a view to making it possible for sysadmins to delete users without having to consult with the client, I'd like to propose two solutions:

1. WordPress disassociates user accounts from authorship information (like in the Automattic plugin ​co-authors-plus)
2. WordPress allows deactivating user accounts so that the user can no longer login or reset their password, but the account still exists

[knutsp]

Delete (deactivate) user account by obfuscation user_login (to ID?) plus suffix -deleted', set user_email to empty, but keep display_name`?

Related to privacy, how users are removed for that concern.