Southwest is an example of general admission applied to airline seating.

By the time you're calling non-middle seats "premium", we've already lost. We should aim to have markets that converge towards abundance rather than maximum extraction through things like price discrimination.

There's no reason to identify with these scumbags. It's indefensible that they sell seats which then aren't actually big enough to fit a person, whether it be their legs or their arms.

There's no airline seat that can't "fit a person", that's hyperbole. Fit any person, maybe. Fit without touching the person next to you, maybe. Fit without negotiating who uses the armrest or shared spaces with a stranger, maybe. I fly frequently, I'm 6'2", I'm medically obese. I fit into a middle seat. Don't love it, it's not the nicest, but it's less cramped than any public transit seat and most theater seats.

By your definition, it would be fine for them to sell the seat that was your lap to someone else, since your body still has enough volume to exist.

I've definitely flown in seats where I had to spread my legs (eg into the aisle) so me knees were not pressing up against the seat in front of me. And no matter which seat I sit in, my arms generally hang over the armrests. Talking about "the" armrest nicely demonstrates how much we've been saturated with this nonsense.

As I said, I'd have no problem if they charged as a linear combination of your weight and the sizes of your seat. But rather the setup is to gouge an outsized price for a comparatively small amount of room, because they'll catch some people at the margins over a barrel.

The idea that everything that can be differentially priced should is really annoying and leads to BS like this where everyone's life is worse to marginally increase profits.