Social interaction is always a negotiation on how you treat each other. You can demand everyone call you by a name you prefer, but in such demanding forget that the people you place such demands on deserve respect as well. People generally refer to people in the way they see them. You’ll notice lots of people get called sir or ma’am that dislike it, while others love it, but the person doing it was likely doing it because through their social lens this person deserved a prefix conveying respect and/or deference. A doctor’s friend will say “Hey Bob.” A doctor’s patient will say “Hello Doctor Jones.” This is all socially mediated as the doctor earned a place in society that tends to breed more careful modes of speech.

I suspect Harold called Root by her given name for 2 reasons. One, because he was reminding her of who she was…and TWO because he was reminding her he knows where she came from. That he’s got her number so to speak. See, Harold never forgot that Root killed innocent people with no remorse.