If someone was hit in the head and got severe brain damage and became severely mentally disabled, would he or she still be the same person as before the incident?
Yes, I agree with you. What clarified in this comment is that we are essentially talking about two different things. You are talking about functioning normally, so of course there is a change after trauma has cause micro-scarring. The normal functioning is damaged. But that's not what I'm talking about.
What I'm talking about is the essential value of the person, that the person's value and worth isn't damaged. It's not an issue of semantics for me. My brain may be damaged, but that doesn't mean that
I am damaged, (damaged goods, as they say).
So a person may have a traumatic brain injury that absolutely damages normal brain function, and normal function on many physiological and psychological levels, but the core essence of the person isn't damaged. This is perhaps not helpful for you, so I will leave it with what has been said.
I guess the difference for me is that I no longer feel like I, myself, am damage goods. Having a brain that complicates my life and complicates my ability to function well does not mean that I no longer deserve to be loved and cared about. I don't feel on any level that I need to heal my brain before I deserve to be in a loving relationship. I absolutely need to be involved with someone who can love me and accept me as I am (to include the broken brain that complicates my ability to function well...lol), but my essential worth hasn't been damaged just because the trauma damaged my brain. That's all I'm saying. :)