Hmmm, um, I always wear underwear at night. How personal to get? Well, lets just say that as a bio-girl, there's stuff going on down there that I don't want smearing around, if you get my drift. I have a fairly large chest but I don't wear a bra. So in summer, nightgown and undies or t-shirt and undies, and in the winter I wear a long-sleeve T with pajama pants or regular pj's.
So, it looks like the general consensus is 'anything you want' 🙂