I may have made the first keymap modification I will undo even after trying it for a while.
Or I may keep it, and grow to find it infinitely better than the Ways of Olde.
What did I do? I moved my shift keys one step in. Before, I got shift when I held down tab and enter (the Corne only has three rows of keys at the edges, so there is quite a lot I want to do with them). Now, I hold down A or the ´ key over on the right side instead.
I figured this would have dual advantages: moving shift to the home position for the pinkies should make it more comfortable to reach, and making tab and enter single-purpose should decrease accidental tabs and enters.
Both things are true, but it takes a surprising amount of effort to adjust to having shift in a different place. (Longer, I suppose, because I still use normal keyboards every now and then.) I especially hit tab instead of A relatively often, and now that tab is single-purpose it fires multiple times when held down, actually making it more disruptive than before. It also takes a bit more thinking because I have to more actively use the right shift now than before in order to comfortably type some capital letters.
All of this is the exact same kind of stuff I went through putting ctrl, alt, and command on the home row, but the disruption somehow feels larger in proportion to the change. Perhaps I am just ignoring and forgetting the work I had to put in?
I notice a very nice effect in that the position of shift anchors my pinkies to the correct resting position quite a bit. I still slide away easily, but I have much more encouragement to return to the right spot and I think that in itself will be a meaningful improvement.
The move also for some reason highlights another quirk of my layout: for some reason I decided to put ctrl, alt, and command in the same order on both halves of the keyboard. It works very well for me, but sometimes when I move between using shift and command on the right side it strikes me how weird it is to have those two functions right next to eachother. I do not think it will make me change the layout, but it is always interesting to see what details my brain latches on to.