Users with bureaucrat rights can manage user permissions. They can add od remove rights from user accounts. Typically bureaucrats are sysops additionally, because the first step to promote a user is to give him sysop rights.
If you want to edit user rights, go to the page "User rights management" (over Special pages)
- Input the user name
- click [edit user groups]
- you'll se two lists:
- left: the groups the user is member of
- right: the available groups to the user
select on ore more items from one (or both) of the lists an the'll change the side if you click [Save User Groups] after having edited the "Reason for change:" field.