By skyforbes 
So, we know that Spartans can be given the same ranks as normal soldiers; (The franchise's protagonist is literally only ever refereed to by his enlisted rank) and yet we never seem to actually see Spartans serving any other role than front-line Infantry. Chief is rarely involved in strategic decisions, usually just doing whatever his current captain orders, and Noble-6 is called "Lieutenant" throughout Reach, in spite of never being implied to have a platoon under his command.
Do these ranks mean the same thing for Spartans as they do normal humans, or is it just an indicator of pay-grade rather than authority?