Played through the Pistis Sophia scene again, trying out all the options as you do. Found out that if you keep disagreeing with him and being suspicious of his motives, there's a point where this happens:
V: No, refuse to let you manipulate me.
Johnny: Huh. Not workin', is it?
Which is... interesting.
I also was reminded that when you answer his promise by saying you'd do the same for him, he has this slightly odd response.
Just this extremely flat, very emotionless "Yeah, thanks."
I don't think that's a mistake. I don't think Keanu misread the tone of the line or there was a lack of direction during recording. With the hindsight that he absolutely will take V's body for a joyride once he gets it, I feel like this scene is very much supposed to be him gently, not without sincerity in parts (because the best lies include the truth, and Johnny is very good at all things charisma skill), manipulating V to get what he wants.
I think the dogtags, the war story, the promise, it wasn't completely untrue, but he deliberately presented it the way he did to get something he wanted. He even led V every way he could to get the "I'd take a bullet for you" admission, which he of course expected and knew he was manipulating out of them, for the purpose of setting up his request to be received as well as possible.
But when V takes it farther than he expected, returning his promise and taking their prior statement from a nebulous hypothetical to a very real declaration about their very real situation, I think Johnny has absolutely no idea what to do with that.
I think that moment is his first pang of regret. I think it's the seed for the talk at the gravesite. I think he can't muster a slick response, this wasn't part of the plan, this wasn't how this was supposed to go.
I mean when they are still out on the balcony and you accuse him, he's angry and has an immediate response. Same with when you thank him, he has a smooth and pretty warmly delivered reply.
But when V says this, his voice goes flat and he barely gets two words out. He goes from leaning forward with open posture and looking right at V to looking away and leaning back, crossing his arms in front of him. And he immediately changes the subject.
Johnny doesn't say *internal panic, existential crisis .exe started*, he says "Yeah, thanks." and I just think that's so beautiful.