I have been having aches in my right arm for a while now, and I am highly suspicious that the backspace key on my keyboard was the culprit. In an attempt to solve the problem, I changed the finger I use for backspace from my ring finger to my middle finger a while ago. The pains lessened, but did not go away completely. As of today, I use my right pinky to press backspace, but with one catch: I ball my right hand into a fist and press the backspace key with my right pinky knuckle as if I were knocking on a door. I find this to be very natural as the skin there is already thicker from it sliding on paper while I handwrite. Also, since my fingers are curled, their tips are above the tab row rather than above the function row while I use the backspace key, meaning that I can return to the home row much more quickly.
Try this and tell me what you think!
Edit: I found something even better. I set the key repeat to fast and the delay until repeat to short. Now, I don't have to spam it because holding it and waiting for it to repeat is faster.
Edit 2: I found a way to not use that wretched key at all. First, I use Shift-Left Arrow to select the unwanted text. Then, depending if I want to replace it or delete it, I either type over it or use Command-X to cut it out.
