Some special powers that give a character certain combat symbols.

MY EARLY ADVENTURES WITH SHIP: Jason of Sparta can use Charge and has "wing symbol".

Question: Since it says Jason "has the Wing symbol," is it not optional? Does the wording prevent him from cancelling the power so he has his regular boot symbol instead?

You can not turn off powers. Powers are always on. There is no such thing as "cancelling" in this game.

Also, 'has' = 'possess', so it's 'almost' as good as being printed on the dial, and it's granted abilities can be countered.