If two bureaucrats both use Special:UserRights to adjust an accounts' flags, their changes do not interleave, but just over-write.
For example, if User:Foo is currently rollbacker, and two bureaucrats each at the same time try to adjust their rights, bureaucrat A by setting Foo sysop and bureaucrat B setting Foo bot, User:Foo should now be rollbacker sysop bot, but instead with either be rollbacker sysop or rollbacker bot depending on whether A or B hit the database first.
This is akin to edit-conflicts. And yes, a very minor enhancement. :-)
Version: 1.21.x
Severity: enhancement