Holy hell, my older sister thinks I'm over-reacting too and she got hit worse than me. She says our parents are good parents and that our mother is a "good, loving mother."

I don't know how to express this (afraid I'll come across as clumsy, rude, awkward, condescending) - I'm glad you tried speaking to your sister (but absolutely not glad she dismissed you) and on PC about this. It takes courage, especially because there's always the fear that you'll be dismissed.

I am...angry that your sister thinks you're over-reacting because you're right - DID doesn't happen with "a couple of wallops". I've searched extensively for case studies involving corporal punishment in my Asian country (because corporal punishment is seen as traditional like how it is in some parts of the USA) and one thing I've read is - people can absolutely develop DID "just" from being switched/caned/beaten. One does not need to have been burned, had bones broken, or suffered violent sexual abuse to develop DID.

Saying this because very often in my country, people say corporal punishment is nothing and "good for you" and "kids these days have no respect because we stopped caning them" and it's "just" a beating...so I spent more than a year trying to dig up case studies where corporal punishment was the main cause of someone's PTSD, DID etc.

I know I strongly believe my generalised anxiety disorder and social anxiety disorder comes from what I experienced growing up (even if my experiences might not meet legal criteria in my nation...) -- because it's rooted in me feeling worthless, defective, bad due to those experiences.