I haven’t done the math, but I suspect that for habitats where gravity comes from rotation, having a wall without a top to hold in the atmosphere wouldn’t work

I haven’t done the math, but I suspect that for habitats where gravity comes from rotation, having a wall without a top to hold in the atmosphere wouldn’t work no matter how high the wall is. That’s because when you move in an antispinward direction your apparent gravity decreases and if you go antispinward at the speed of rotation your apparent gravity is zero. Fast moving particles that are bouncing every which way are going to randomly have zero gravity a significant fraction of the time and just drift away. Liquids don’t do this because they are bound together through surface tension and other mutual dipole attraction forces and solid objects of course have all the atoms bound together, but gasses I’m pretty sure would just float away.