Q:

Should a user be able to change another user's role to match their own? 

Lets say a web application has four user roles.  Standard, Supervisor, Manager and Administrator. 
Should a manager be able to promote someone else to a Manager, or only to a supervisor? 
I realize in the latter situation, an admin technically wouldn't be able to make any other admins, but administrators could always be an exception to the rule. 

A:

Although it is up to you, common way is a user can set other users equal to them. 
There can be many admins if it is wished to be so..
Giving a lower rule is a harder case in my opinion.. I made you admin and you can un-admin me?  weird huh?  well...this could happen...
So yeah, I can set you equal to me, than you can downgrade me. 
Thus, having only one master user is safer.  Not that there can't be many, but having a lot of them may lead in to using your app/website etc...

