I don't fault the actors in "Mark of Gideon" given what they had to work with.
The best performance was by the fake
Enterprise, which was just one of the story's idiocies - even a Federation member
planet would have a hard time faking a whole large starship well enough to fool its captain for even a microsecond.
Gorshin redeemed his approach to Bele by the way he said "I once heard that on some of your planets people believe they are descended from ...apes."
Even Kirk sometimes pronounced a name in two different ways; in one episode he pronounced Kyle as "Cowell" throughout.
EDIT: Hey! I finally made Commander!