I have repeatedly added the same user using the web interface, however it simply will not stick after a reboot.
I have also created a DB in the setup menu directly after creating all my users. Not sure why it wont save them to the hard drive after creation. It seems to stick for the admin user, but other settings simply arent there.
Before of adding any user or making configurations you should create and activate a database. After the activation, the system will be automatically rebooted and at this point any change will be permanently stored.