Oh, oops -- I promised to answer this a while ago and didn't. My answer overlaps a lot with this one, but I'll add my own perspective here.
My experiences are colored by a few aspects of my background and I'm just one person, so it's hard to isolate gender specifically. So let me just list them up front:
- I'm a woman.
- Professionally, my background is in male-dominated tech, so early on I had to learn to "run with the guys", so to speak. (Think programmer culture.) I have experienced (blatant) gender discrimination in the workplace.
- I began my Jewish learning as an adult. I have no yeshiva background. I usually need the vowels when reading Hebrew.
- I don't belong to an Orthodox congregation, though I'm aware I probably should based on what I believe.
- In person, I find it hard to push my way into conversations. I'm an introvert, not overflowing in social aptitude, and keenly aware of how much I don't know. It can be awkward and embarrassing to speak up or ask a question sometimes; there's always a part of me that thinks "hey, I ought to know that already; this is a dumb question". Even when I know I'm a pretty smart person and I've double-checked my reasoning before speaking.
- Online, I find it a little easier to jump in (many of the social barriers are absent or different). But online interactions have other challenges, especially in the presence of negative feedback (which people are more willing to type into a textbox than say to a person's face).
Are those last two points gender-correlated? I've heard people claim it; I honestly don't know. I spent some extra "ink" on them to describe the actual context in case it's not really about gender at all.
I shall now proceed to ramble in the general vicinity of your questions.
What has your experience on Mi.Yodeya been like?
Very positive, but sometimes individual posts or comments make me cringe. (I'll talk more about the cringing on a later question.)
Mostly I don't think about gender when I participate here. I don't feel I'm being treated differently because I'm a woman. I feel like my contributions are weighed and evaluated the same as if my user name were "Moshe" and nothing else were different.
In reality, though, unless "Moshe" is a ba'al teshuva or ger, he's probably better-equipped to answer halacha questions than I am and will probably outscore me. If we were only a halacha site I wouldn't be as engaged, but because we also welcome questions about text, traditions, and practical "how-to" matters, there's stuff I can contribute.
All that said, my reputation points and the "warm fuzzies" that accompany them are more hard-won and dear to me here than on any other site on the network where I've bothered to make an investment. (There are sites I don't invest in because of how they treat beginners and newcomers.) It's not that it's about the points; if we didn't have a reputation system at all I think I'd still be here. But we have it, so of course I notice it and notice how much of a hard climb it can be.
I don't think most of my experience here is tied to my gender. I do agree with another answer that my gender affects my learning opportunities, which in turn affects what I can contribute here. Starting to take all this seriously as an adult, rather than from birth, means I missed even the more-limited opportunities that would have otherwise been available to me growing up as a girl.
Does Mi.Yodeya sufficiently address the Jewish questions and concerns of women? Are there any female-specific practical or halachic concerns about posting here that should be brought to the community's attention?
There are questions I can't ask here, and they're the same questions I can't ask my rabbi either (super-embarrassing in person!), which means I don't ask them and get proper answers anywhere. But I don't know how we could change any of that, given that we're operating on the public Internet. And I don't think we've gotten too many questions on the wrong side of the modesty line that weren't also p'sak questions, which we would rightly close anyway.
I think there are some specific categories of questions that women are more likely to ask than men, that can't be asked here, but they're hard to ask anywhere so we're not unusual in our handling of them. I suspect there are similar questions that men are more likely to ask, too.
Could the community improve its behavior in any ways with respect to gender issues, or any other concerns that affect female users in particular? How?
This is where I come back to that cringing I mentioned. Too often I see comments that read to me as unnecessarily confrontational. They make me uncomfortable anywhere, but they make me especially uncomfortable when directed to new or low-rep users. That's not about gender, but one gender tie-in is that if the user is a man who's had a learning background where argument and confrontational styles are normal, he might be more likely to shrug it off or see it as normal. The exact same comment directed to (a) someone with a strong yeshiva background and (b) someone with no formal learning is likely to be received differently. Since I, as a reader, don't know who's (a) and who's (b), I cringe for the possible (b)s.
I've written before about comments, commenting style, and gentle vs. harsh correction, so I won't belabor the point. (Maybe later I'll find links.)
What is your opinion on why there aren't more women here, and what can we do about it?
I think some of it's background and can't be helped; large portions of our site content are only interesting to people who've reached some level of Jewish learning and enjoy it, and many women never got that level of learning that was standard curriculum for their male peers. We skew toward experts, and experts overwhelmingly skew male.
Some women have reached that level, and I think they'd have an experience here that's comparable to men's if they came here and participated. I don't know how we would reach them. I don't feel like we need to change our gender balance or go looking for them, but I'd be delighted to see more of them here.
For what it's worth, I found the site when Joel posted about it in Joel On Software. Hmm, maybe technical women who already have to "run with the guys" are a better target than the broader population?