physicsforums, gamedev.net, stackexchange, arstechnica observatory, and so on, those are all more rational than LW.

Can you list some specific examples of irrational thinking patterns that occur on LessWrong but not on those communities? The one guess I can make is that they're all technical-sounding, in which case they might exist in the context of a discipline that has lots of well-defined rules and methods for testing success, and so less "bullshit" gets through because it obviously violates the rules of X-technical-discipline. Is this what you mean, or is it something else entirely?