Treasure: I personally think that the question of sex should be rather irrelevant where it doesn't concern clear-cut differences between females and males (anatomical for example). That is, I don't think my gender is important or has anything to do with my life or my hobbies or anything similar, but only affects me regarding my anatomy and such stuff. Since videogaming is a hobby, the gender thing should remain largely irrelevant. For one reason or another, it isn't in general, but in this forum, outside of giveaways for females or dicussions about feminism, the gender little matters. And that's good imo.
At any rate, to the question now. Even though the avatars I use tend to be something a girl/woman would choose (I like cute pirates/vampires!), most of the time when I gave something over at open this thread I'd receive some thanks via pm that were like "thanks man" or "thank you sir" or something similiar (the rest of such messages were gender neutral-aka just saying "thank you" or anything similar). I didn't correct them, largely because it was irrelevant and also, why should I correct them? Who cares if I'm a male or a female really? Does it matter? All that matters is that all of us like videogames!
And not only that, but also I feel somewhat flattered, in the sense that "Well, my sex isn't evident-to the point of someone getting it wrong! And that's how it should be!"-why not let them think I'm a male? Since one can't see people behind the screen (how they look like etc) he can't really make an assumption based on anything else than the avatar-which means that one can form the way he's being portrayed by others just by picking an avatar. I personally pick avatars that I like, but more precisely avatars that I feel portray well my inner self. What works for me is the cute pirate-girl/vampire, but other things work this way for other people.
In short (as I wrote a whole thesis answering a simple question), I don't correct people if they get my gender wrong because I don't think gender should matter. You, however, are an entirely different person and thus, you should do whatever you feel like doing regarding this aspect-be it correcting people or not-whatever you feel like doing. After all, why should women reveal themselves just to prove non-casual gamers exist? Aren't there enough surveys proving that? But I guess that's stereotyping for you-and you shouldn't give so much attention to what you're called, if it doesn't seriously bother you.

P.S. After refreshing and seeing the answers added while I was writing mine-I agree with what saith32 just said. :-)

Vythonaut: I'm the exact opposite. I like to know who is who, after all we are all friends here! :-)

Crewdroog: thanks treasure, that was a really great and thoughtful read. Like I said, I really never cared until it was talked about in the ddickinson thread. maybe i'll tell the little feminist voice in my head to shut up and just enjoy myself. :)
Crewdroog: and this is also an excellent point. maybe i'll just correct people half the time ;)

Crewdroog: Guys, if people were calling you a girl (in a not mean way), would you correct them? Have you corrected them?

Crewdroog: So, is it better to correct or just say f- it and let people call you whatever they want? Guys, if people were calling you a girl (in a not mean way), would you correct them? Have you corrected them?

Luned: *waves over at forum sig/title line* I try to give others the relevant info with a bit of humor. I'm not offended if someone uses a male pronoun to refer to me on the internet (it's not like they can see me or hear my voice), but I may correct them if I'm in the mood. It's as much a matter of courtesy towards others... I'd prefer that men not assume that I can fully understand certain aspects of their life because they think I share their "plumbing", when I don't. Similarly, I don't expect anyone who hasn't actually been pregnant to fully understand that whole experience.

saith32: Man when my wife was pregnant she was crazy. All happy to have a kid with me then all of a sudden crying and eating and threatening to cut me if I don't bring chocolate home after work. I love our son but I think he is going to be an only child.

Crewdroog: lol. oh jason mewes....

penumbren: I tend to correct people if they obviously call me a guy. If it's a random "Thanks, dude!" I don't, because that's so generic these days. As I've gotten older, I have to say that sexism bothers me more and more, and the automatic assumption that gamer = guy is definitely that. Most of the time, I try to correct people with either a straightforward, "Nope, gal over here" sort of thing or a joke, because it really is the sort of thing that can set people off... but I'd rather irritate someone than have them assume for a year that my genitals involve dangly bits, because that annoys the hell out of me.

Not that I think genitals of any sort should have any part in gaming, but they obviously do, what with gamergate, tropes, etc. Those things are exactly why I've started caring about other people's assumptions. I've gamed since I was 10, and we're coming up nearly to three decades of it now and I'm proud of it, dammit. :P

saith32: Man when my wife was pregnant she was crazy. All happy to have a kid with me then all of a sudden crying and eating and threatening to cut me if I don't bring chocolate home after work. I love our son but I think he is going to be an only child.

darthspudius: The man is a comedic God! lol

saith32: Having a kid is pretty cool to me. Yeah there's moments to where it can get frustrating but overall having a kid is awesome. For me anyways.