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It seems that if the karma incentive was reduced on political articles, people would have less incentive to post the thoughtless ones.

This is backwards. Usenet had political flamewars despite having no karma.

People post to political threads because it makes them feel good to stick up for their particular causes. Emotions that reward us for signaling our allegiances and general loyalty are one of the cognitive adaptations that allow our species to solve the Prisoner's Dilemma to benefit from cooperation, specialization, and trade.

Start reading Robin Hanson: http://www.overcomingbias.com

or Comeuppance: http://www.amazon.com/Comeuppance-Altruistic-Punishment-Biol...

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