It's quite common in electric cars these days. Makes driving much more pleasant, and once you get used to it there's minimal need to swap back to the brake pedal.

Neither had I. I've heard of clutch braking, where you downshift to slow the vehicle, though that won't bring it to a stop. Truckers use that sometimes because it saves wear on the brakes, and it's banned some places. I suppose regenerative braking could have a similar effect, but why not have that turn on the brake lights the same way pressing down on a brake pedal does?

I believe in the past year or two someone passed a law with a specific deceleration amount. If you were decelerating at or beyond that amount, brake lights are required to come on. Maybe the EU? Can't quite remember. Would definitely be good to have that here in the US

That amount of deceleration can vary a lot from car-to-car.

I had a rental recently that would just keep going and going when I released the accelerator. I could be going 65 mph, release, and 30 seconds later, still going ~60 mph. As someone that used to drive manuals and now drives and EV, I hated it. My typical driving style is built around the idea that the brake pedal is an evil device that converts cash into brake dust and waste heat, so I use it as little as possible and release the accelerator earlier when I'm going to need to stop. That doesn't work on a car that barely slows down at all when you release the pedal.

I don't know if this was considered a feature for this car, or if maybe the throttle cable was too tight or stuck or something, but I hated how much more I had to use the brake pedal.

Most ICE vehicles with automatic transmissions (aka 90% of them) either explicitly open the clutch or do torque converter things when off throttle, the result being that the vehicle starts freewheeling. Air resistance and friction and what not means the vehicle will eventually stop, but in a modern car at highway speeds that stopping distance can still be multiple miles; and that's before you bring hills into the equation.

My point being for most people expected behavior is for a car to only slow down during active braking and maintain momentum otherwise, and trying to change that otherwise would bring more danger than it's worth.

Sharing the road with drivers on an entirely different control scheme is something I am not a fan of. Going from 2 axes of control to 1 axis of control is not a change to be trivialized. Some in the commercial trucking industry would argue that allowing 2 pedal driving was a catastrophe with regard to filtering out low skilled and unsafe drivers.

Cruise control whenever feasible and safe is probably the most polite solution to the consequences of one pedal driving. The freeway is where this kind of driving causes the most frustration for me. I don't think it should be banned but I think drivers should really give a shit about how they impact others around them. We can make it entirely about safety if that helps. At some level being polite aligns with basic physics.