Some ""sociopathic"" traits I like to give Alastor in my writing:
He likes eliciting reactions out of people, frequently in a sadistic way but not only. He likes when he can get exactly the reaction he wants; he likes when he doesn't know how someone will react and gets to see an answer to that question; he DOESN'T like it when he expects one reaction and gets another, even if the difference is in his favor in some way.
He is very intellectual about the way he reads people. There are multiple overlapping classification systems, there's an ongoing observations folder, there is to some degree non-stop experimentation in small ways (see above). There are very few assumptions Alastor is willing to make and be the least bit confident in.
Reading a room / crowd dynamic is a lot easier than reading an individual interaction for him. It's just what he specializes in, and he finds it simpler, with major factors easier to keep track of and confounding outliers smoothed out.
Individual reactions of people Alastor doesn't personally know are frequently completely unexpected and opaque to him. He cannot guess in advance how people will see him.
Because of this, he likes to pile on affectations and be as over the top as he can, to at least statistically make his image in other people's eyes more predictable. Controlling his reputation on a large scale makes individual interactions more controllable in turn.
I really have to reiterate point 1: Alastor DEEPLY enjoys being a scientist of other people's behavior. Every small moment of having his expectations confirmed or learning something new where he didn't have a preexisting assumption is a joy. He notices and he has fun.
Between this gap in predicting unfamiliar individuals' behavior and Racism PTSD, Alastor is, in fact, afraid of people. He likes his personal space, he doesn't like crowds, he doesn't like unfamiliar mass social situations. He is always on guard and always ready to disappear - funnily enough, his fight or flight response is heavily tuned towards flight. He's just good at controlling it / not letting it show.
There is a middle ground of "close acquaintances" where Alastor is most comfortable with people. Cross over that gap into "friends", and he's lost again, because that's the point where people start to get to know "the real him" and not just the image he painstakingly crafts, and he has no idea who that person is or how to be them. His mishmash of principles, preferences and fears is opaque even to him and might as well be a random number generator at a close enough distance to bypass the filters. Because of this, Alastor avoids close friendships - he simply doesn't know what to do with those! Presenting a coherent facade is crucial to his ability to navigate social interaction.
When Alastor DOES want someone's good opinion, which happens far more easily than he'd like, he has no idea where it's reasonable to draw any boundaries whatsoever. He grew up in a close-knit poverty-defined community where everyone helped everyone with everything unconditionally regardless of personal opinion or relationship, and that's the default he doesn't quite know how to correctly tune away from. What his mama taught him never quite lined up with how other people treated him, which ended up with his sense of normal being VERY blurry and unhelpful. Sometimes he'll be excessively rude and sometimes he'll be absurdly accomodating and he never knows where the exact boundary is.
Because of the above difficulties with getting information across in either direction, it's always easier for Alastor to do something himself than ask another person. Manipulating someone into doing something is a safer and more controllable situation than asking them - who knows what they'll assume or misunderstand? Not Alastor, that's for sure. It's easier to present a carefully crafted lie he knows how to sell than try to get across how he actually perceives reality at a given moment.
Basically, his comfort zone is at the intersection of "I'll do anything for you, just let me know what you need" and "easily spooked cat". Needless to say, that's a very vulnerable position to be in, so... he does not do that! That's why his favorite social mode is "observing from the shadows". Spooked cat: currently safe.
