Loyal, Honest, Frank, Sarcastic: These are some words which can be used to describe Jayne. Others include, Frustrated, Flabbergasted, Irritated and I swear I'll club him to death in his sleep.
There's a reason why Jayne is still on Scorbs ship, and it isn't because he enjoys the conversation.
In spite of his obviously superior skill, Tactical abilities and combat prowess he remains Ascorbius' trusted right hand man, often being the difference between life and death.
He got Ascorbius through flight school - something he sometimes regrets; and his family connections have gotten them both out of trouble more than once.