I don't understand what people here mean by "B."
Seems they're referring to Bayesian Epistemology / Bayesian Confirmation Theory, along with informal variants thereof. Bayesian Epistemology is a very well respected and popular movement in philosophy, although it is by no means universally accepted. In any case, the use of the term "Bayesian" in this sense is certainly not limited to LessWrong.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
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