Mainstream meaning the people with credentials that the Holden was referring to (whose views are somewhat echoed by everyone else). The kind of folk that will not be swayed by some sort of mental confusion between common discourse "the function of the AI is to make paperclips" and technical discourse where utility function is mathematical function that is a part of specific design of a specific AI architecture. Same kind of folk, if they come across the Russian mathematician name-dropping that's going on here, and after they politely exhaust the possibility that they misunderstood, would be convinced that this is some complete pile of manure arising from utterly incompetent person reporting his awesome misunderstandings of advanced mathematics he read off a popularization book. Second order bad science popularization. I don't even care about AI any more. It boggles my mind that there's entire community of people who just go around having such gross lack of understanding of the things they are talking about.
edit: This stuff is only tolerated because it sort of promotes interest in mathematics. To be fair, even very gross misunderstanding of mathematics may serve a good function if a person passionately talks of the importance of mathematics he misunderstood. But once you start seriously pushing nonsense forward - you're out. This whole thing reminds me of experience with entirely opposite but equally dumb point: some guy with good verbal skills read Godel, Escher, Bach, thought he understood Godel's incompleteness theorem, and imagined that understanding of Godel's incompleteness theorem implied that humans are capable of hypercomputation (beyond Turing machine). It's literally impossible to talk sense into such cases. They don't understand the basics but they jump ahead to the highly advanced topics, which they understand metaphorically. Not having had properly studied mathematics they do not understand how great is the care required for not screwing up (especially when bordering philosophy). That can serve a good function, yes: someone sees the One Truth in, say, Solomonoff induction, and someone else actually learns the mathematics, which is interesting in it's own right even though it doesn't disprove God or accomplish anything equally interesting.
I'm worried that LW doesn't have enough good contrarians and skeptics, people who disagree with us or like to find fault in every idea they see, but do so in a way that is often right and can change our minds when they are. I fear that when contrarians/skeptics join us but aren't "good enough", we tend to drive them away instead of improving them.
For example, I know a couple of people who occasionally had interesting ideas that were contrary to the local LW consensus, but were (or appeared to be) too confident in their ideas, both good and bad. Both people ended up being repeatedly downvoted and left our community a few months after they arrived. This must have happened more often than I have noticed (partly evidenced by the large number of comments/posts now marked as written by [deleted], sometimes with whole threads written entirely by deleted accounts). I feel that this is a waste that we should try to prevent (or at least think about how we might). So here are some ideas: