It is not so easy to separate assertions and evidence, Logos01. An assertion is in itself evidence - strong evidence perhaps, depending on who it comes from and in what context. Evidence is entanglement with reality, and the physical phenomenon of someone having said or written something can be entagled with what you want to know about in just the same way that any other type of evidence is entangled with reality.
For example if you were to ring your friend and ask him for the football results, you would generally update your degree of belief in the fact that your team won if he told you so (unless you had a particular reason to mistrust him). You would not wait until you had been provided with television footage and newspaper coverage of the result before updating, despite the fact that he had given you a mere assertion.
That is a trivial example, because you apparently are in need of one to gain understanding.
If someone quotes Yudkowsky as saying something, depending on how impressed you are with him as a thinker you may update on his mere opinions (indeed, rationality may demand that you do so) without or before considering his arguments in detail. Authorities may be "unreliable", but it is the fallacy of grey to suggest that they therefore provide no evidence whatsoever. For that matter, your own sensory organs are unreliable - does this lead you not to update your degree of belief according to anything that you see or hear?
Since Yudkowsky is widely respected in intellectual terms here, someone might quote him without feeling the need to provide a lengthy exposition of the argument behind his words. This might be because you can easily follow the link if you want to see the argument, or because they don't feel that the debate in question is worth much of their time (just enough to point you in the right direction, perhaps).
On the other hand it is true that argument screens off authority, and perhaps that is what you are imperfectly groping towards. If you really want to persuade anyone of whatever it is you are trying to say, I suggest that you attempt to (articulately) refute Yudkowsky's argument, thereby screening off his authority. Don't expect anyone to put your unsupported opinions together with Yudkowsky's on the same blank slate, because you have to earn that respect. And for that matter, Yudkowsky actually has defended his statements with in-depth arguments, which should not really need to be recapitulated every time someone here references them. His writings are here, waiting for you to read them!
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.