On Special:ManageWiki/permissions user removes all permissions for
groups "user" and "*".
Now he checks Special:ListGroupRights but discovers for "user":
are still listed.
These rights are not allowed to be unset by bureaucrats per Miraheze.
This is largely due to the requirements imposed by having global accounts. Certain features would break or be locked out if certain rights were not permanent, specifically those in the * and user group you have discovered.
Also no control over
makes one worry that there is no way to turn off editing.
(But in fact it doesn't take priority over other permissions, so the worry is not real.)