urbanspaceman:

Headcanon: it takes Spock a long time and it’s very difficult for him to learn that human buddy teasing/badinage is fundamentally different from the verbal nastiness leveled at him by Vulcan peers when he was a child.  That’s why his interactions with McCoy in TOS occasionally take on a note of real unpleasantness.  

But eventually Spock grows to realize that human emotional motives and expressions are far more complex and varied than Vulcan ones, and he learns to judge humans’ teasing based on different social criteria than his former tormentors’ bullying.  He eventually even gets the hang of teasing his friends right back.  

I second this headcanon!