It's unsettling to see Snape fidget. He doesn't like having to think about the other man in terms of who he was as a person. Who he is as a person.

Harry knows he doesn't have the memory to be a good liar and as he sits here, being watched, he tries to recall just what he's said or done that would prompt this particular flavour of distrust. It could be just good caution, but his gut tells him otherwise. The only lie he can recall is not divulging that he was the final horcrux, but Harry is quite sure that was a polite falsehood for both of them.

"I don't think there are people we know, or beings that we'd recognize as 'people' in the depths of the ship. I think, that when we go 'home', we're turned into protein-based goo and flushed into space rather than experimented on in some other, deeper lab." Isn't that a cheery thought?