I think that if a "straight" man wants to wear womens underwear for anything other than it being a "bedroom" game - a woman, one that perhaps is involved with said man may get the impression that he is not "straight".
Lets be real here - female underwear is designed for female genitalia - we sit.
Boxers or other male underwear has that convenient opening - they stand up.
The real question is why would a straight man want to wear it?
More than likely it could be a sexual fetish such as the desire to wear his desired ones panties already worn by her.
There are a myriad of reasons why a man would want to do this that range from a bet with friends to pleasing his partner to something more deviant in nature.
Whatever the reason, depending on the underwear itself, our panties, bras, g-strings and thongs are not always the most comfortable things in the world and we don't have that "package" to cover up - lol.
So, comfort it cannot be about - Good topic though, maybe I should write a Hub about it. *smile*
Have a great day,