I don't understand how you can consider holding shift more effort than reaching out to backspace. When you work with JCS - or nearly any other program that doesn't require you to write too often - one of your hands should be on the mouse and the other one in the shift area for the most important hotkeys: - in JCS they're B, F, E, ctrl+E, shift+E, shift+T, ctrl+S, ctrl+Z, ctrl+R, occasionally number keys. Backspace and comma are then between your hands and unreachable by either. Meanwhile, B and shift are right under your fingers.
That reminds me, obviously it would be difficult to work without these in the level window, but I always wondered - is there anybody who uses them in the tileset window? I don't, because setting it up feels like a waste of time and I don't use event tiles that often, and when I do I often want to give them parameters.