Blocky icons aren't masculine. You can't show me a man shaped like that. But blocky figures are just not that good at conveying femininity, and in the absence of femininity the default assumption holds.
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Earlier you argued an icon Antx posted isn't truly androgynous because it has features which enable it to be seen as feminine - but at the same time you're arguing that because I can't show you a man shaped like a block, that therefore this isn't a masculine trait. Obviously I can't show you a woman shaped like Antx's icon, so what's up?
I think the problem is, you're arguing color and shape have nothing inherently masculine to them, which I agree with - I think it's sociological conditioning. However, masculinity is in itself defined by society. The fact is, our society considers certain colors, and certain shapes, to resemble the image of a man moreso than a woman. Likewise, there are certain traits which bring to mind the image of a woman moreso than a man. I think arguing about that is much beyond the scope of this discussion, which is whether your icon is truly biased or not. The fact is, the following pixel figures are completely genderless, but a slightly sharper angle and a different colour completely changes the gender we'd associate with them: http://imageshack.us/photo/my-images/8/capturexll.jpg/.
We'll never prove this without a time machine or a portal to a parallel universe, but I'll bet if I'd started with a figure that had a four-pixel waste and thinner arms and shoulders and presented that as my gender neutral icon I'd have people (possibly some of the same people!) telling me it's too feminine to stand in for the sort of male figure that might be swinging broadswords around.
Of course, the game's premise is in and of itself biased. We are sociologically conditioned to believe an adventure game needs a masculine hero (whether male or female). There is nothing socially odd about associating masculinity with a powerful warrior, which is what your image seems to depict.
What you're missing is that we live in a society where *no hair*... not "the explicit depiction of no hair" but "no explicit depiction of hair"... is read to be the same as "short hair".
And "no articulated hips at all" is read to be "narrow hips" rather than "hip width unspecified".
A chest with no features at all is seen to be a chest that specifically has no female breasts, not a chest that lacks both male and female identifiers. The missing male identifiers are less... protuberant... but they're still missing.
If you're not getting this I really don't expect you to ever grasp the fine point on the chest, but just look at male iconography re: hair. If you've never thought about it you might think "Okay, well, baldness is more typically seen as a male trait so the generic male stick figure is bald." But as the xkcd examples (or the "short hair" on my icon) demonstrate, that's not really how it works in our culture.
In the world we live in, no depiction of hair whatsoever == no information about hair conveyed == default hair == "male" short hair. That's not a side effect of the fact that long hair is short hair and then some. It's about marked and unmarked cases.