If you need to flip your spacebar then you need to review your position/ergonomics in front of your desk.
Have any facts to back this up?
I use 3 different desks with 3 different chairs and the height difference changes from desk to desk, I always prefer a flipped space.
What facts? It's basic ergonomics. You should be positioned relative to your desk so that your elbows form a 90° angle, your forearms and wrists should be strait and your hands should hover above the keyboard (and a wrist-rest is for resting the palm of your hands when your are
not typing). All in a relaxed position. Unless one has some kind of deformity, in this position, your thumbs should fall down on the top of the space bar — not on the edge/angle. If so, you are doing it wrong.
Not saying it is your case; there might be something else in your setup(s) that could be a potential issue, but for instance a lot of people I see typing with inverted spacebars tend to have their wrists at an angle, wresting them on the desk while typing. That's asking for trouble in the long run if you spend a lot of time in front of the computer.
