Regarding categories, I must be missing something. Found no reference to a field called category_nickname in 1.5.2 or 2.0 either in the database or in the code.
As for the user_nicename vs. user_nickname:
In 1.5.2 both user_nicename and user_nickname were in the wp_users table. user_nicename was the sanitized (I think that’s the right word) version of user_nickname meaning “My Nickname” is made into the nicename of “my-nickname”.
In 2.0, user_nicename is still in the wp_user table but it is the sanitized version of user_login field. The nickname field was moved into the wp_usermeta table with a ‘meta_key’ of ‘nickname’. One interesting point is that when a new user is added (or registers) the user_login, user_nicename, and nickname fields are pretty much the same value (except user_nicename is sanitized). Subsequently, the nickname can be changed by the user or the administrator.
In 1.5.2 the ‘nicename’ was tied to the ‘nickname’ so that meant that the ‘nicename’ changed if the ‘nickname’ changed. But, in 2.0 the ‘nicename’ is tied to the user_login field so the ‘nicename’ nevers changes because the user_login can never change. Don’t know if that was intentionally done by the developers…
One other note–if your plugin is using something like the get_userbylogin function, the ‘nickname’ is NO LONGER accessed with the variable user_nickname; use nickname instead. But, user_nicename is still valid. See Author Templates for more info on this.
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