Personal comfort is, as you say, an individual thing. I'm not saying you're wrong to not like something, just clarifying as someone who wears a watch to bed every night that it isn't sweaty.
Both my wife and I wear ours and it's never a problem and mine is never an impediment to having my hand under my head either.
Personally I just think there is far too much data that the Watch collects overnight for me to not wear it. I have also taken to putting it on my nightstand charger when I get into bed, while I read or watch TV, then putting it back on when I want to go to sleep. That may be a solution to your concerns as well.