Never. I exclusively use my left thumb for the space bar, too.

I could probably type faster if I fixed those issues, but 30 years of bad habits die hard.

My keyboard has two shift keys. I don’t think I’ve ever used the right shift key, not even for usage with emulators for consoles with a lot of buttons… the modifier is always the left shift key since it’s closest to my left hand and I can have my right hand on the other side where the arrow keys are. The arrow keys, WASD, Z, X, A, S, Q,W, 1, 2 etc have always been sufficient for most games.