Ever think about how it makes so much sense for Vash to have even more dissociative symptoms than those we see?
Like. His body was handled extremely violently against his will in a situation heavily mimicking assault twice. After one incident he had severe memory loss and constant nightmares and flashbacks, and after the other he was so gone from himself that he could do nothing but wander around in what could easily be described as a fugue state (and for all we know wasn't even responsive when Lina found him). He was kept in a tiny space for fucking months on the ark, that can't not fuck somebody up.
And Vash is full of heart. He bears to have space to witness and remember and be affected by the people that he meets even after 150 years, even after this much hurt. And he does so decidedly. For someone like him, having to constantly put his emotions aside in order to handle whatever dire situation at hand, having to put his grief on hold 'cause he just has to jump into the next fight, must take a whole lot of compartmentalisation.
The thing is, he seems okay with closeness most of the time, even initiating it, and in that context it's so easy to imagine all this trauma hitting him when he least expects it. Someone happens to touch him in a way that mimics an Incident a little too much and he just goes Blank. Or his body refuses to listen to him, refuses to move at all or moves on autopilot against his will, or he feels numb when he should be feeling so much, when he's used to feeling so much, and he's unable to tell anyone what's wrong when asked, or so scared 'cause Fuck, what if his body or mind that he already has no regard for betrays him when people need him the most?
And I bet he'd hate it even more than the average guy, 'cause he loves being around people, both by nature at this point and deliberately, and he wouldn't care about himself nearly enough to try to figure out his own triggers, not when he'd have to decidedly relive everything in the process just to learn how to be kinder to himself, but being unable to predict when your mind's gonna do you in is Terrifying. man.