Why don't you have a left-handed Thermapen?
Interesting question. My wife Suzette is left-handed and she's always thought the opposite. She prefers to use her dominant hand to wield the roasting pan, grasp the food with tongs, stir, or whatever else she's doing in combination with the one-handed temperature measurement. Thus, in her opinion, it's best to hold the Thermapen in her right hand while she uses her dominant hand for the other tasks.
Don't buy that? While the Thermapen isn't quite as ambidextrously switchable as a screwdriver or a hammer, it's pretty close. It can easily be gripped in a number of ways. I hold my Thermapen in both my left hand and right hand depending on what I'm doing. Still I empathize with anybody who's left-handed and wishes the Thermapen were reversed. So, if our engineers can ever figure out a no-cost way to do that in the next Thermapen, we'll consider doing it. Meanwhile, switch-hit.
–Randy