The sessions you turned down - was the language barrier bad enough you feared limits would not be understood?

Interesting to see your enjoyment being dependent on full understanding as well.
But as long as the session language is one in which the Domme is most skilled, I think there can perhaps be an upside to the sub's experience. Her superior language skill can reinforce her supremacy over the sub, and hence add to the sub's experience. (Not sure it will make up for the awkwardness resulting from misunderstandings, though)