I hope it is not too late to add to this topic.
I have had experiences where my gender was unknown (not asked for) when contributing or commenting. I don't think my gender has any great bearing on what I am expressing. The question of gender never came up nor was it required to contribute in the place I refer to. It was just a fairly open and free place where people basically went to have a good old uncensored work rant. Or share humorous experiences etc. And so, there was a great deal of freedom to be silly, and no cencorship for anything but the obvious things that should not be tolerated.
My intention was never to hide my gender, it just never came up and I never really thought about it. It was, however, available to anyone who looked at my original profile where I had indicated it. In the one instance where I actually referred to my gender (about two years into being a member), there was a reaction of surprise. It was very strange, because I had never gone out of my way to not mention it, however, apparently had not done so. It just didn't seem relevant to anything I was expressing, and in some weird way, I expected that people would know.
There are definately preconceptions around gender and how each reacts or expresses themselves. I think knowing it influences how you perceive the message or opinions of someone. I'm not saying it is a bad thing, because there are differences in the way genders express themselves. And if you don't know it, you will automatically assume one way or the other based on your preconceptions.