As for physics, I was thinking more about this whose negative karma I have already commented on. In the meantime I have forgotten that the post managed to return to zero afterwards.

"Low-quality" is too general a justification to recognise the detailed reasons of downvotes. Among the more concrete criticisms I recall many "this is off-topic, hence my voting down" reactions. My memories may be subject to bias, of course, and I don't want to spend time making a more reliable statistics. What I am feeling more certain about is, however, that there are many people who wish to keep all debates relevant to rationality, which effectively denotes an accidental set of topics, roughly {AI, charity donations, meta-ethics, evolution psychology, self-improvement, cognitive biases, Bayesian probability}. No doubt those topics are interesting, even for me. But not so much to keep me engaged after three (or how much exactly) years of LW's existence. And since I disagree with many standard LW memes, I suppose there may be other potential "contrarians" (perhaps more willing to voice their disagreements than I am) becoming slowly disinterested for reasons similar to mine.