Not sure if anyone has pointed this out yet, but this moment right here:
Others have pointed out how this scene outlines Kylo’s mistake. He realizes that he screwed up by abducting the girl, rather than the droid as Hux points out. However, there is something I’ve noticed from the first time I saw the movie that I haven’t seen anyone else point out yet.
At first, Kylo looks surprised. He whips around, not expecting to see Hux there. As soon as he turns back around, he looks down as if trying to hide his face. Then he seems to accept Hux’s presence, lifts his chin and sturdies himself.
To me, it seems as if he’s regretting having left his mask in the interrogation room. Snoke has known Kylo Ren from when he was young, back when he was still training with Luke to become a Jedi (as Leia points out in the novelization), so Kylo probably feels comfortable showing his face to Snoke. However, for all we know, this could be Hux’s first time seeing Kylo’s face at all.
His reaction to being seen without his mask here is much different from the way he acted just several moments before:
The writers made an effort to underline the subtext that Kylo Ren removing his mask was an intimate moment. It’s not something he does often. Even when we see him sitting in his room, monologuing to Darth Vader’s helmet, he’s wearing it.
So I think it’s interesting that he appeared so confident in revealing his face to Rey, and yet the moment Hux sees his face, he’s regretting himself.