I really (honestly) am not trying to start a grammar flame war, but I
don't see how your change is an improvement upon what was there...
I guess the point here is to let the "only" refer more specifically to
the _user_ executing the action, and not the _action_ that is being
executed.
The previous version might have been interpreted as "the super-user can
only set or unset, while all other users may also toggle or increment or
do whatever else they please".
Or is the infix "only" even more ambiguous in that it may refer to
either its left-hand operand or its right-hand operand?