I don't have the general problems with reading, but I do have the problem you mentioned. And I'm also kind of a speed reader, I think the problem is here.

My mother made scrapbooks for my siblings and I with samples of our schoolwork over the years.

If you go back and look at early examples of my handwriting, every "S" was backwards, my b and d were often flipped the wrong way, as were my p and q.

My spelling was atrocious, but my vocabulary was way above average.

I also had the issue with transposing numbers while doing math.

It wasn't until I reached High School that I had a teacher who recognized dyslexia when he saw it.

As sibling comments say, this is a common feature of learning to write that doesn't indicate dyslexia.

One of my relations wrote completely mirrored for a time, that was interesting. It did make me wonder if their brain was flipping the entire World; they've corrected it now. It reminded me of, da Vinci, who I think write in mirror writing for himself but used regular writing when writing for others.

Up to a certain age, the S/b/d/p/q issue is considered normal. I certainly did it through early elementary school, and since I have ADHD, I've been screened for dyslexia enough times to be fairly confident I don't have it. All 4 of my kids still did this at the end of first grade, with only one to go on to be diagnosed with dyslexia.

I think flipping and mirroring letters is just using our ability to see that the shapes are the same. You have to do some unlearning in a way, or rather recognizing that rotating a shape changes its meaning.

Yeah, I think most people don't read words, but recognize their shape, first and last letters being most significant. That's why it is relatively easy to read text with words internally scrambled. Unusual names, long words that are first learned from text, misread once and remembered like that forever. This is especially easy if you don't normally pronounce words while reading.

I still have to double take on "invertebrate", because I originally read it as "intervertebrate" or something like that :).

That's funny. I see that happening with some words or names especially (I can't remember an example I realized the other day).

It might just be that the brain "shortcuts" some things and change the way it's perceived. Insertion of an r in some places is an actual linguistic phenomenon (more on the Otellini case).