Continuity mistake: In "Amok Time" Spock described Vulcan mating rituals as "a thing no out-worlder may know" - here he goes on about them with Droxine at some length.
Continuity mistake: The leather strap with which the Troglytes lasso Spock disappears and reappears repeatedly from around his waist and shoulders during the scuffle at the mine entrance. (00:04:30)
Chosen answer: If they're in orbit, they're being pulled along by the planet's gravity well, therefore, impulse engines would only be used for minor corrections and would be "on standby" while in orbit, but not active. (Like keeping your car idling without revving the engine and creating plumes of exhaust).
Captain Defenestrator
Thank you for the info.
Movie Nut