Mere assertion.
A given statement is either true or not true. Authorities on a given topic can be mistaken; and as such no appeal to an authority can be, absent any other actual supporting materials, treated as a rational motive for belief. In all such cases, it is those supporting materials which comprise the nature of the argument.
Here's a good example: Richard Dawkins is an expert -- an authority -- on evolutionary biology. Yet he rejects the idea of group selection. Group selection has been widely demonstrated to be valid.
Authorities on a given topic can be mistaken; and as such no appeal to an authority can be, absent any other actual supporting materials, treated as a rational motive for belief.
P(X is true | someone who I consider well-educated in the field of interest stated X is true) > P(X is true)
LessWrongers as a group are often accused of talking about rationality without putting it into practice (for an elaborated discussion of this see Self-Improvement or Shiny Distraction: Why Less Wrong is anti-Instrumental Rationality). This behavior is particularly insidious because it is self-reinforcing: it will attract more armchair rationalists to LessWrong who will in turn reinforce the trend in an affective death spiral until LessWrong is a community of utilitarian apologists akin to the internet communities of anorexics who congratulate each other on their weight loss. It will be a community where instead of discussing practical ways to "overcome bias" (the original intent of the sequences) we discuss arcane decision theories, who gets to be in our CEV, and the most rational birthday presents (sound familiar?).
A recent attempt to counter this trend or at least make us feel better about it was a series of discussions on "leveling up": accomplishing a set of practical well-defined goals to increment your rationalist "level". It's hard to see how these goals fit into a long-term plan to achieve anything besides self-improvement for its own sake. Indeed, the article begins by priming us with a renaissance-man inspired quote and stands in stark contrast to articles emphasizing practical altruism such as "efficient charity"
So what's the solution? I don't know. However I can tell you a few things about the solution, whatever it may be:
Whatever you may decide to do, be sure it follows these principles. If none of your plans align with these guidelines then construct a new one, on the spot, immediately. Just do something: every moment you sit hundreds of thousands are dying and billions are suffering. Under your judgement your plan can self-modify in the future to overcome its flaws. Become an optimization process; shut up and calculate.
I declare Crocker's rules on the writing style of this post.