I was thinking about something similar. I am under the impression that a lot of problems around DPDR are about over-using rationality to fix every problem. This was certainly my strategy even before I had DPDR. It's like these obsessions confuse my subjective experience with rational objective truth, as if they could work together. But they are really not the same thing and don't go on the same plane. For example, existential questions try to find rational definitive answers to things that are just part of our subjective experience, and it's trying to put predictable concepts on things that constantly escape rationality. Very often when we try to make them really work together, they enter in conflict. Solipsism, for example, seems to me like an attempt at finding an agreement between the two, and saying that maybe objective truth is absolutely aligned with my subjective experience and they are the same thing, "there is objectively only my experience and nothing else".
But they can't work together, because they are not even in the same reality. An actual experience and a theory are really not the same thing. But strangely enough that's kind of what DPDR feels to me, it feels like my actual experience is experienced on the same level as just a thought, it's as real as a thought.
I have talked about narcissism before, and interestingly, in psychoanalysis, the definition of narcissism is like the newborn, in it's first development stage, which doesn't understand the presence of people around him. Only his own experience exists and the satisfaction of its needs. It's not that he is hungry, for him it is just that there is hunger. At some point there is what they call the "narcissistic wound", where (I'm not sure about all this definition - don't quote me) they realize that others exist too and they don't share the same needs as them. To my understanding, narcissist wounds, even for an adult, are kind of the same thing as traumas (but don't quote me on this), and it has to do with the realization that we are not as powerful as we thought, or the realization of our true limits. So the baby realizes that their needs are not necessarily met, and they start to define who they are, and separate themselves from the rest of the world. So there is something about this that deals with the mix between subjective experience and objective truth and how we separate the two.
At an adult age, what we generally call a narcissist, is someone who thinks they are always right, and others are just there to serve them. It's like they confuse their own opinions and needs for an objective truth that others should naturally accept, because they have a wrong construction of themselves. Changes in how they view the world and how they separate objective truth and subjectivity might directly question their sense of self and how they built it in early childhood, and it can feel like dying. One experience I had about 6 years ago, that I think felt like a panic attack, came from suddenly realizing that I had built a castle of rationality and theories and it could not hold anymore and was collapsing. I had found many explanations to kind of mix and tape together my subjective experience with safe, rational and solid objective truth, and suddenly I acknowledged that it didn't work (because it can't work), and it all collapsed, and I really felt almost like I was dying. Changing who we are at the core can be a terrible experience, in my opinion. And I can't just tape a wound that is inherent to how my self is built right now.
By the way, I realize that my father's death when I was 15 might have affected me more than I previously thought. My sick relationship with my narcissistic mother might not have helped me build a good sense of self, and this is 98% of what I had to talk about in therapy for years, but my father's death might have been something I was not built to accept. Even before his death, I remember that before ten, I had regular problems sleeping in the evening, because of an existential fear of death. I thought that even if it will come in a long time, it is so impossible to wrap my head around it, and so impossible to accept. I feel it's like I had constructed a maladapted self for whom death is not something that fits in the story. And at my father's death, I think I got this impossibility that was just too hard to adjust too. It feels like I need to change my sense of self to adjust to the fact that death is a part of our reality. It is so fundamental to me that I feel like I won't go beyond that without a huge panic attack. Or maybe the answer is something totally different. A friend of mine used to have panic attacks with fear of immediate death, and it all stopped when she just dared to talk about it to her boyfriend. So it felt like fear of death but deep inside it might have something different, so I don't know. But it feels like this is a big thing for me. And I would like to change. The most horrible thing would be that I find a rational explanation to fix this wound without changing my core self. It would be like extending my stay in my mind prison.