[krona]

High conscientiousness correlates with agreeableness; it's rare to have a highly conscientious, highly disagreeable person who would actually go out other way to offend others. So I don't think that's that's the explanation.

Further, commentors on any particular subject are, I think, statistically more likely to be monomaniac obsessives, and that correlates with poor social skills (e.g. truth-seeking at the cost of empathy). In other words, autism.

[ScottStevenson]

Fair point, but it correlates more with Neuroticism. Conscientious people could be agreeable because they tend to believe "what's in the water", or the dogma of the place and time. This could cause them to be disagreeable with those outside their tribe.