Nice question. The meaning of flags is defined in qa-include/qa-app-users.php with binary(bit). In the case of test, I change direct flags in command-line or phpMyAdmin of MySQL. The specific field (related password) in the qa_users table is binary. When you change flags in phpMyAdmin, you must never use GUI for editing specific record. You have to change it by UPDATE phrase. If you change flags of specific record by phpMyAdmin GUI, password hash will be broken, and, user can't log in to your site.
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