This Could Be Completely Wrong And I Honestly Wouldn't Even Be That Mad - Tumblr Posts

A lot of people are saying that this is a happy smile or a smirk... I don't see it that way. We compare N to a golden retriever a lot so...

This is what I see, a dog baring teeth. I see this smile as A: an intimidation tactic and B: a "mask", a way of hiding what they really feel.
More evidence for this is that V makes this smile a lot and J almost NEVER makes this expression, the only time she does is in the pilot during Uzi's presentation.
For most animals, baring teeth looks like anger to us. In the case of murder drones however, it looks like sadistic joy. In BOTH cases, what we see isn't fully true.
Whatever that smile means, I'm willing to bet that it isn't happiness.
Edit: Just noticed, it's only a half "smile", he's trying to suppress it.