Our snakes are not getting pissed off, but are defending themselves which is instinct. When feeling threatened they show behavior which many people are portraying as emotions. This is anthropromorphising and this has caused dangerous situations with wildlife in the past. I am not claiming that it will with our herps, but it could.Here are my thoughts, Ive only had a snake for 2 weeks but bare with me. I believe if it can show a preference of what it likes and doesnt like, and also get pissed off and annoyed which are emotions, then I can guarentee that it can love. Anger, hate, and fright are all emotions, if you can feel one then I think its safe to say you should be able to feel them all. Just my 2 cents.
The bottom line is they are not feeling emotions. They are acting on instinct.
As for recognizing certain people. This is easily explained. Each of us have our very own unique chemical scent, that only our herps will pick up on. If you are regularly in contact or near your snake, they may eventually realize you are not a threat. Though if another person, which will have their own chemical scent and would be foreign to the snake, the snake may act in a defensive behavior, which some have marked as an emotion.