This issue is much less about psychology and much more about thermodynamics. It's not OK to sweat all night long. If the guy's metabolism runs hotter than his partner's, he really needs the space in order to sleep well. The letter writer should get an extra blanket and a body pillow.

It's all very romantic to think that cuddling all night is the ideal, but it's just not nearly as important as getting a good night's sleep. And anyhow, I'm not sure why anybody would want to cuddle with a sweaty, sleep-deprived partner. Imagine cuddling an infant with colic and a fever.