An Unforeseen Advantage of Different Shift Systems?

I wish I could say I purposely set up each of my four bicycles with unique shifting mechanisms, but it's simply not true. I, like many others, have multiple bikes because of their various advantages for preferred riding styles. It just so happens, for example, that older mountain bikes had thumbshifters; my Rivendell came stock with thumbshifters setup inwardly; a Peugeot UO 14 has downtube levers; and my Dahon folder came with Grip Shift. Whatever the setup, it surprised me, with a recent thumb injury, that only the Dahon allowed me to continue riding with minimal stress to my thumb. I simply allow the questionable thumb to hang while the rest of my digits control steering and braking - easily done on a folder's shortened grips. When I shift, my index finger controls the shifting while my thumb is barely used. 

Once again, the versatile Dahon Boardwalk saves the day.