I do that deliberately. I came on here many years before the gender discussion started and I was very aware that this was an opportunity to be genderless. I wanted my words and thoughts to be the most important or governing factor in my online encounters here, not my gender.
It's been really interesting, over the years, to observe how posters respond to me based on their assumptions. Butchersapron, for instance, seemed to assume I was a wet soggy bloke, unworthy of his engagement. If he thought I was a woman, he'd have engaged with me more generously. I had a long time to watch and learn from his style of response to others in order to draw this conclusion.
Some people have asked me directly, some have said they don't know and prefer it that way. I suspect some posters move between thinking I'm a woman and then changing their mind. People on here who do know have always done me the courtesy of preserving the ambiguity.
It's been really liberating.