The dining room rule dress code varies. You usually have to have nipples covered, but that rule is very flexible. It depends on the group/groups there during any given period of time. I have seen women be asked to cover up in the dining room and have also saw women eat dinner almost topless with nipples fully exposed. Like anything else at Hedo, the rules are never constant.
I find it odd that women can't show their nipples, but I have seen several men eat in the dining room in just a towel around their waist. Go figure