Sweetheart, the navy calls the people in that position helmsmen. The kids in the official navy press release was refered to as either master helmsman or by his rate of quartermaster or quartermaster third class.
... who've been there and done that ...
If you insist on "conning officer", then back it up with something beyond a simple personal statement.
is just a cranky old swabbo! Pay him no heed!
I have another possible reason why Spock was most often called "Mister," or just "sir": That's the way he preferred it!
Bear with me here. I got the idea from an early novel, The Entropy Effect
, where Spock makes an announcement to the crew. It was an extremely serious announcement, so he referred to himself as "Commander Spock."
Uhura finds it out of character, and remembered that he frequently referred to himself mainly by his positions, either First Officer Spock or Science Officer Spock.
Based on this, my theory is as Spock was raised Vulcan, he's essentially a pacifist, like other Vulcans. Although he's in Starfleet, he prefers to think of himself by his positions and not his rank, with is too militaristic for his pacifist sensibilities, despite the fact he can use force when logic and the demands of the service require it.
Just my two cents, people.