I don’t think they should ever refer to Kylo as Kylo Ren. They are all Knights of Ren, so the Ren is implied.

Anyway, I think the fact that Ben doesn’t say a word during the final confrontation is an issue, if we have the other knights constantly talking to him. He should have some sort of one word response to “What? How?/That’s not fair.” when he does his nod. Do you think it would work with his existing lip movements (or rather lack thereof)?

KoR: “What? Is that Skywalker’s lightsaber?”

Ben: “Yup.”

Something like that.