Actually there r quite a few people doing it in camp, commanders
included
That doesn't mean that it's right for you to do it as well.
If any of those commanders ever got a heat injury, and he was
found to have worn a shirt on the inside, you can be sure that his
backside will be buttered good.
Like I said, you can solve the problem without creating another
problem. Abrasions can be avoided with durable plasters in problem
areas.
Don't be a goondu to risk heat exhaustion just to avoid getting
minor abrasions!