Speaking as someone who has suffered exactly the same injury as in the picture, I can tell you that it wouldn’t have happened if I’d had a riving knife in my old Unisaw. It happened to me for the first and only time after 20 years of working with a table saw. I pushed a small board through the saw, it turned into the blade, and I got walloped in the gut. I now have a nice little hernia where it tore my stomach muscle. I’m darn lucky it didn’t hit me in the face.
As for removing the riving knife, I have these thoughts: Unlike European tablesaws, riving knives in American saws are mostly retrofits. The manufacturers just tacked on the riving knife to an existing design. The saws weren’t designed from the ground up with the riving knife in mind. As a result, they can be can be clunky and get in the way, or not work at all, like when using a stacked dado. (The Sawstop’s design looks to be much better, but I don’t have as much experience with it as I do older tablesaws.)
However, I agree the riving knife is the best way to protect all woodworkers (not just inexperienced ones) at the tablesaw. The default state of our tablesaws should be to have them in place. If a member ever removes one, they should be required to put it back.