First off, kudos to you for creating a new thread just for this topic.
My apologies if it appeared in the other thread as though I were attacking you. The closed captioning reference was genuinely something which had been working its way into my consciousness for some time now. I only mention it as I can well see that being a limiting factor in improving one's reading/writing skills.
Somewhat orthogonal, but I still feel is relevant: My first wife's mother was born and raised in Germany. As such, she was a young schoolgirl still learning basic grammar and writing when WW2 kicked off. I used to read letters which she wrote to my ex and would be astonished at her writing/grammar skills, or lack thereof. Her writing was atrocious (looked like she'd been riding a bus at the time) and she was lacking any sort of punctuation, inconsistent capitalization (and in German, any/every noun is supposed to be capitalized), no paragraphs, so every letter looked like a stream of consciousness where you'd have to do on-the-fly edits in your head in order to make sense out of them.
And yet the same woman was very articulate when you spoke with her. And she would read German newspapers and magazines, so she was definitely being exposed to the right stuff on an ongoing basis.
(Aside: my handwriting sucks; I write with my right hand, my mother is left-handed, my dad's dad was left-handed, and my dad did a number of things with his left hand, and I do do a number of things mainly with my left hand, such as using the knife at a meal; it's possible I may have been strongly encouraged to write with my non-dominant hand, hence the sucky handwriting.)
Another anecdotal story: I recall many years ago stumbling across some 20-something woman's blog, long before they were ever called blogs. She was deaf (born deaf I think) and her writing skills were brilliant. So I can't say I'm convinced that deafness automatically translates to less-skilled writing abilities.
What I *will* buy for a buck is the possibility that the German measles may have directly impacted your ability to learn language. This isn't a criticism as much as it is a point of concession. Over the many years that I've studied other languages (epecially early on), I know I've seen other students who really struggle with those other languages. Some people just aren't wired that way.
I do recall one time you made a rather heated post in response to a similarly-themed discussion, and holy crap, as far as I remember, it was on the freakin' money as far as spelling/punctuation/grammar were concerned. Which made it all the more baffling; if you could do that once, why couldn't you do it always? Although I would certainly recognize that if it's more challenging for you to do it that way (eg, spending 5 times as long to polish up a post), then I can certainly see why you wouldn't want to expend the extra effort. There are times I'll really put in the extra effort in polishing up writing (like recently, when I helped a friend do his resume), but it really can be taxing.
I realize you have had to learn quite a bit about how you got to where you are today. And I can certainly appreciate the hurdles you've overcome, and can definitely understand how old this sort of petty focus (at times, what seems like "picking on you") can become.
What isn't clear to me is how you perceive the rest of us perceive your writings. I can't speak for anyone else, as I feel I'm more sensitive to typos/grammar mistakes than certainly a certain percentage of the populace (there's some atrocious stuff out there in forum-land), but a single typo can leap off the screen at me; a stream of typos starts to appear to my eyes like noise would be to my ears. Unfortunately.
I'm trying to come up with an adequate analogy. Remember, this isn't to convince you to change your ways, as much as it is to help you understand where at least I'm coming from. You've done a spectacular effort at explaining where you're coming from, so it seems only fair.
If I have a face-to-face conversation with most people, the chat is quite natural. This is how I see most posts on the BEA. But when I read (most of) your posts, 3d, it's like the person I'm speaking with is doing something distracting at the same time as he/she is speaking with me. Like banging a couple of trashcan lids together, or jumping up and doing the Riverdance. It's distracting. Could I carry on a conversation like that? Well, I *can*, but it becomes quite a bit more challenging. My efforts to understand also feed into my feeling that I'm not being understood, so I end up expending more effort trying to be understood myself, as well.
Again, I hope you can take this post for what it's meant to be, which is an acknowledgement of the challenges you've faced, and a (hopefully) complementary response to help you see it from another perspective. Again, not to change how you write, simply to help you see something which I don't really think you see presently.
You've earned more than your fair share of battle scars just being part of the human race, and are no doubt that much more weary for it. I tip my hat to you for making the effort to explain this in a "big picture" way.