Female-only hackathons are what's wrong though. It implies that women cannot compete at the adult table, which is untrue, but if you treat people separately this is what registers in the collective subconscious. Similar to affirmative action making a lot of people think less of academic achievements depending on race, because it was handed to someone. This becomes a problem for those who don't need AA to be competitive, but have to face the stereotypes of the group they're in. Something like affirmative action should be about poverty, not race, because poverty is the underlying reason why people start at a disadvantage. Similarly with hackathons (I'll admit, I'm a guy who never went to one) the problem isn't that women can't compete, but that they're not attracted to these events for some reason. This has more to do with social dynamics. If you're male and a lot of males are going they will advertise it to their friends. So what we need would be more advertisement of these events geared toward women, with no effect on who gets selected.
(We're reading a blog post written by a woman kernel developer, for what it's worth).
Even worse than forfeiting competition, and particularly sad if women themselves think so.