If your wrist is in contact with the edge of the laptop while you are actively typing, then your typing style has a good chance of giving you RSI. You'd be better off trying to fix that than trying to make the fast path to RSI more convenient.
How the f are you supposed to type? Ideally I'd like full support for my arms from the elbow to the wrist.
In my first job - i think it was in 1997, I had my own small room with an L-shaped desk with a rounded corner. That gave a few inches of space for resting my arms - both when typing on a quite reasonable Pentium laptop, and especially when using the mouse.
Since then, the desks and the chairs has become shittier and shittier. Except perhaps when a was a consultant for an HR-department.
The U-shaped desk was probably the best ergonomically designed workplace I've had. Maybe a wheat-filled pad along the desk would have made it better.
If your arms are resting, then your fingers and wrists are doing the maximum amount of reaching as you type. If you use a wrist rest you are encouraging your fingers/wrist to reach up (bend in your wrist) instead of neutral or reaching down (more natural position).
Constant change in position, dynamic motion, strong & brief muscular exertion of whole hand and arm, even including the shoulder vs constant static position w/ small repetitive motions, where the fingers really are doing almost all the work.
You should try to avoid continuous static load on your muscles, especially the smaller ones. So you should find a typing position where that doesn't happen. You also want to use your muscles in the strong and comfortable part of their range of motion, which depends on the entire chain of joints, because tendons have to stretch past several joints to get to whatever bone they attach to – so for fluent finger motions, you want to keep wrists and hands in as neutral a position as you can.
If your wrists are not straight while typing a lot, that's really bad. I constantly see people typing with their wrists either significantly flexed or significantly extended; doing that a lot is a fast road to RSI, and even doing it a little is pretty unpleasant and inadvisable.
If you are going to type a whole lot at a stretch (say, as a programmer or writer), you want your arms to be mostly passively supported from the shoulder. Having your arm bent at the elbow doesn't cause much strain, as long as the upper arm is hanging loosely down with your shoulder relaxed – so bring the keyboard relatively close to your torso. Resting your wrists, palms, or forearms on some surface and then typing generally causes more strain than having your wrists and palms "floating" above the keyboard while actively typing. You can rest the fingertips lightly on the key tops if you want. You can rest your palms on a palmrest or arms on an armrest (or table, or lap, or whatever) while you are taking a break from typing. It's generally a good idea to take regular breaks.
There doesn't appear to be good evidence that this is better for RSI. I found one study that shows greater shoulder and back strain when doing the hover hands approach. It might make more sense for piano since you need more mobility up and down the keyboard, but for typing your hands don't need to move nearly as much, so resting should be just fine. The do suggest some sort of support under your wrists, though.
Huh, seriously? Have you ever worked in an office? Perhaps your mental picture of what op is describing might be misaligned? I just always assumed it was a rarer/ more disciplined style some people had
On a modern laptop, the keyboard is on the top half of the lower case these days, not the bottom.
My palms are hovering over or resting on the chassis, and I sit high enough that my wrists do not come in contact with the edge of the case or desk. The majority of the weight of my arms is supported by my shoulders. For me, the ideal height happens to be pretty close to a neutral wrist position.
A more concrete way of putting it is if you are putting so much weight on your wrists that the edge of the MacBook is making you uncomfortable, you're probably doing it wrong.
I've heard this but I've personally been typing this way for 25+ years (wrists on the rest, including on laptops exclusively for the last 15) and my wrists are fine. Meanwhile people I know with ergonomic keyboards and everything that's supposed to save your wrists are the ones with bad wrists.
The reasonable takeaway from that correlation is that people with preexisting issues turn to ergonomic keyboards to avoid worsening those issues, not the other way round.
While this is true, if standard keyboards were bad then everyone who uses them would have issues, yet many (most?) don't.
Sometimes I think it comes down to actual typing technique. For example. I've heard of "Emacs pinky" which is easily avoided by simply using the Ctrl key opposite the key being pressed (use right Ctrl for C-c for example). I religiously never use Ctrl, Shift or Alt + another key with the same hand and I feel that's been huge. Also my elbow, wrist and hand always form a straight line to the keyboard with a standard laptop keyboard and the right body position/desk and chair adjustment.
After RSI years ago, I switched to an X220 and had 100% the opposite experience. The curve at the front of the case was a perfect resting point for the heel of my (average size) hand to allow easy reach of the keys. I replicated this geometry by sanding a pine 1x4 and wrapping that in soft leather for a wrist rest with a procession of mechanical keyboards (currently a Lenco Majestouch 2). Literally decades later, all is well.
If your wrist is in contact with the edge of the laptop while you are actively typing, then your typing style has a good chance of giving you RSI. You'd be better off trying to fix that than trying to make the fast path to RSI more convenient.