He definitely picked up on the fact that Finn was uncomfortable. But this was over romantic feelings, not their First Order past. So instead of getting awkward right along with Finn, Armitage simply smiled. So.. it was complicated, was what he gathered. But that wasn't to say that the feelings didn't exist and out of those feelings, jealousy was undoubtedly one of them.
Armitage inched closer. Not that he was trying to crowd Finn. It was more that he realized this was a conversation that shouldn't have been shouted across the room, especially if Finn was getting anxious. "You're not being unreasonable, you know. You and I come from two very different places within the First Order, but neither of us were encouraged to care for other people. Very much the opposite. Without Rey, without Poe, I still wouldn't know what that's like. I imagine it's something similar for you. But Finn, just because I'm involved with them doesn't mean that you should feel ostracized. If you claim that you have no say in their relationships, then neither do I."