I did a quick google search and found that women are more risk adverse than men (at least in financial decisions - that's what most of the studies were about). If that generalizes to social situations, then women would have more fear of disapproval of their comments than men, independent of their intelligence. (I've talked to people who say they are scared to post because they think they're not as smart as other LessWrong users, but I don't know how common that is.)
I don't think it's just because of the karma system. People here also aren't shy about telling others when they're wrong, so even without a karma system, people will worry about the response more than they do on most other sites. I think it's really important that we tell each other when we disagree, so it wouldn't be worth removing that. Maybe we could change how we tell each other, but I'm not sure what form that would take.
Today's post, Of Gender and Rationality was originally published on 16 April 2009. A summary (taken from the LW wiki):
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