I feel very similar, and it used to be worse before. I think it is related to a weak sense of self. It's part of other diseases like borderline personality disorder, I think. Something that is hard for me too, is to define my personality. If someone gives me a compliment, it's like it goes through me, because my personality cannot let itself be seen or defined by me, so I don't know if people could be right or not about me, it's like I don't know what they are talking about. So it's not that I don't have a self or a personality, because for sure I have definitive personality traits, but it's like I have a weak relationship to my own personality. I think it's normal for people to act different with different people, like at work or with this or that group of friends, but they wouldn't say they have a different personality. They would still think they are the same person, but just act different according to context, which is pretty healthy. But for me it's like how I act with this or that group starts to define me or it overrides any weak prior image of myself that I could have, so it could be like I have a separate personality for each group. Personally this has been going better and better over the years, but it is still a bit present, and I think I see what you mean.
I also have some kind of black and white thinking towards people. They can be nice, but then they do something mean, and I just hate them, and I think "oh, now I see their true personality", and I would either do nothing about it, or sometimes just cut ties with them or become very distant. I think it's a little similar in a sense as the previous point. It's like one bad thing they do overrides the previous image I had of them and I can see only that. So usually I have to let some time pass, so that the mean thing they have done gets diluted in the rest. But in general I can overreact a bit and then change my mind.
It's like this kind of information, about who I am, and who others are, and what is the current state of my relationship to them, are stored in a place that I can't really access because of DPDR. In the same way I could have strong anxiety about work, because as soon as the person wasn't physically in front of me, I could imagine anything about the relationship to them, or what they might think about me. It's like all my past experiences of good interactions with them, or them saying they are satisfied with my work, could not be accessed, so I couldn't imagine anything.