Re: Maybe a silly question, but...
You don't need to know.
The same response that's accepted without question when addressed to a man, may be inappropriate when addressed to a woman. The obvious example is if it makes some jokey mention of bodily functions or sex, but there are more subtle differentiators too. When talking face to face, we unconsciously adjust to our audience. Online, we don't have the information to do that.
(Not that we should, of course.)