If you come up with a body shape and context and I guarantee you we can come up with a more comfortable way to position the laptop than anything requiring wrists bent downward.
This is not about the design of the Macbook: the same goes for any other laptop, however smooth and soft its front edge might be.
You also shouldn’t drive your car into other cars. But we still put seatbelts and bumpers on for those who do.
I said people who are digging their forearms into their laptop edges are probably bending their wrists down in a way that puts strain on the tendons used for typing (not to mention putting direct pressure on the tendon sheaths for the finger flexors), so they should be careful about RSI.
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.
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.
Ideally you shouldn‘t be putting any significant pressure on any surface with your forearms, palms, or wrists while actively typing. You want your hands “floating” with the fingertips resting very lightly on the key tops. But even if you must rest your hands or arms on something, please keep your wrists as straight as possible, and especially avoid wrist flexion or extension.
The surface of your laptop should be more-or-less parallel with the plane of your forearms, with the keyboard kept close to your torso so that your shoulders can remain relaxed with your upper arms hanging down at your sides. (This reduces the torque your arms put on your shoulder, allowing you to comfortably support your arms without any need for external props.)
If you have a tall desk and a low chair, and can’t change furniture, the way to work around the poor furniture design is to either (a) move the laptop to a low tray or directly onto your lap, or (b) prop the back side of the laptop up so that the base of the laptop is tilted toward you, with the keyboard parallel to your forearms. Keep the laptop (or whatever other keyboard) near the edge of the desk.