Okay, I've got a few thoughts here.
1. Flame has a point. You could've taken this among another sample group instead of running the locals around here like lab rats in a maze.I not saying what you did was morally wrong, but in psychology, it's usually bad form to experiment on your mates (buddies, not shagging partners. pardon my anglicized antiquated terms.).
2. This sort of experimentation is a vital part of the internet, and one of its greatest strengths. Everyone has a large amount of conceptual existence. My actual self and my theoretical self are two entirely different personae. For all you know, I'm an old half-sober Irishman with a bad haircut, or a Kenyan relay runner who as too busy taking care of his mom to the Olympic trials.
3. To argue one of your points, "Gender" is in essence a culture, albeit not necessarily innate. It's also a cultural value. Why? Because humans make it that way.
4. As for the flirting thing, some of s don't really "flirt," we just joke. I'd need specific examples to take this further, but some of what you interpreted as "bad flirting" may have just been "random prattle."
5. Although I'm glad this was a learning experience for you, it's a little odd to claim it as more than that. Personally, I've played on both sides of the gender line, and neutral, and honestly, I don't remember any real different treatment. But I'm also a guy who tends towards more gender neutral/even areas and games on the internet, so that changes the overall attitude. I mean, when the gender ratio isn't 3:the rest of the room, we tend to act like adults or kids.