On a muddy ride the steel deore thumbshifter mounts have a tendancy to bend forwards, especially on the front shifter dues to the extra pressure required to shift
They don't. At least not in the same form as the Deore (XT) ones. I've heard some people talk about rapidfire as thumbshifters before though and, while technically you do use your thumb to shift with, they're not what most people would think of.