Excellent review of an ever-contentious issue. One thing I learnt (ouch) in my last pass through grad school is that I'm a dinosaur. I'd double-space between sentences on Medium if the text editor allowed it, and all right will always have a space in the middle when I spell it. But at least I no longer correct others for taking the other path, though I do still bridle when they insist I'm in the wrong.

To the prescriptivist and descriptivist I would add one other player, which is the brain. We all learn grammar (and usage) long before we are exposed to grammar rules. When something "just sounds wrong" to your ears, it is because it violates a pattern your brain learned and saved, probably at an early age. Back in the 1950s and early 60s, my schoolmates and I thought Ebonics was a joke, but it isn't, it's a tightly-structured and rule-bound dialect of American English, and the one that millions of people grow up using until their teachers tell them it's all wrong.