Is there a reason Spock, Scotty, Sulu and Chekov are referred to as "Mister" as opposed to their rank? We have ranked officers like "Captain" Kirk and Lieutenant Uhura, as well as descriptive names like Doctor McCoy and Nurse Chapel. Was this Roddenberry's attempt to demilitarize Starfleet bt emphasizing "Mister" over ranks like Lieutanant Commander or Ensign?
"It was formerly the custom to introduce officers below the rank of Commander as 'Mister.' Now it is the custom to introduce all officers by rank, but you may speak to them or of them as 'Mister' when they are below the rank of Commander."
Like Kirk says in "The Wrath of Khan" (to Kirstie Alley's character): "Prayers, Mister Saavik. The Romulans don't take captives."