"Girl" isn't a pejorative unless you're determined to take it that way. It has nothing to do with age; it's part of an informal nomenclature, as in "girls and guys". I know many women who refer to themselves as "girls" -- including those in their fifties and sixties -- and/or use "grrl" in their online names, and there are even groups like LinuxChix which use "chicks" in a hip sense rather than a belittling one. "Girls' night out" is another example. I would even observe there's an inflection point where women above a certain age prefer the term and consider it a compliment to be referred to as such, as youth and vitality are desirable connotations.
And groups of women do refer to wanting to find more "boys" -- the terms "men" and "women" both seem to connote some kind of stodginess, probably because most people's models for what men and women are, growing up, is parents, teachers, and other authority figures, all of whom are tragically unhip.
Have you ever had a serious job with female coworkers? I'm going to guess "no," since your entire post is nonsense.
First, you are referring to informal situations. But, this is (supposed to be) a professional setting, and the rules are much different in a professional setting. Generally, you want to refer to the femininity of women as little as possible in a professional setting, and when you do have to refer to their femininity, you must be extra formal.
Here is the rule I go by: never call a woman a girl in a situation where it would be inappropriate to call her a bitch (she better be a good friend). And, never call a black man a boy because it is almost as bad as "nigger."
If you don't understand the reasoning behind these rules then you should find a good friend to explain them to you very carefully.
Sounds like you worked with some pretty uptight people! I would suggest buying them copies of Spice World. And no, "Hacker News" is not a professional setting, it's certainly informal. "Women" is itself a loaded term to many feminists, who may prefer "womyn", "womun", or some other spelling.
In order for "girl" to be insulting, you must subscribe to the notion that there is something wrong with being young and female. Accepting that premise is to unwittingly agree with perpetuating a worldview in which the very notion of female-ness is disempowering. "Girl Power" actually challenges the establishment; suppression of any reference to femininity reinforces the older male status quo.
That so many people are programmed to think "girl" is insulting just shows how far society still needs to go to free itself from counterproductive paradigms.
> never call a woman a girl in a situation where it would be inappropriate to call her a bitch
Your implication of equivalence is loony, and of course more evidence for the informality of Hacker News. Your post also suggests to me a useful reason to use the terms "girls" and "boys" -- to smoke out people who get offended so easily or are stuck with such old paradigms that they clearly lack the flexibility needed to work in a start-up. Valuable co-founders aren't stuck with old thinking, are hard to offend and easy to joke around with.
I didn't post that just to be PC, I posted it because I felt that in that context, "women" would have been a preferable, more respectful term, even though I wholeheartedly agree that English is a bit lacking in that it forces you to choose between "girl" and "woman", neither one of which is ideal. I would have erred on the side of respect, though.
Italian has ragazzo/a, which can be used both formally, and informally, for anyone from their teens to early thirties. It's far superior to the dichotomy that English forces upon us, but be that as it may, "girls" is probably left to women to use amongst themselves as they see fit.
And groups of women do refer to wanting to find more "boys" -- the terms "men" and "women" both seem to connote some kind of stodginess, probably because most people's models for what men and women are, growing up, is parents, teachers, and other authority figures, all of whom are tragically unhip.