Yes this is true, but many of those ways put considerable strain on their hands and wrists and commonly lead to serious injury. If the forearms are digging into the corners of the laptop, that almost certainly means that the wrists are extended (bent downward), which puts the tendons/joints used for typing into a weak and injury-prone part of their range of motion.

People should do whatever works for them and listen to their own bodies, but should be really careful with computer keyboards. I know many professional computer-users who did themselves serious harm with significant impact to their careers.

If something hurts even a little bit, please don’t try to work through the pain.

Sometimes the pain is caused by a razor-sharp laptop edge, which is the point of the post. I type in two main positions–on my back like an otter, or lying face down on a mattress. I'm guessing some people here type suspended upside down from a gravity swing. The computer case design shouldn't punish us for our typing choices!

Lying on your back or lying face down or suspended from a gravity swing are all fine (albeit perhaps not ideal for very long stretches).

In none of these cases should your forearms be digging into the edge of the laptop. If they are something else is wrong about the position.

I occasionally type sitting on a couch, lying on my back on a bed, sitting at crappy furniture at a coffeeshop, sitting on the floor, with one hand on a tall table while tending to toddlers, etc.

In any of those contexts, it is possible to find a way of typing with straight wrists.

This really has nothing to do with the computer case design; the previous poster should adjust his or her posture irrespective of laptop choice. RSI is no joke.

Look, it gives me satisfaction to rest the heels of my hand on the edge of the laptop. I feel more alive when I do it. Colors are brighter. Back off!