How is an outsider going to tell if the people here are the best rationalists around? Your post just claimed this but did provide no evidence for outsiders to follow through on it. The only exceptional and novel thesis to be found on LW concerns decision theory which is not only buried but which one is not able to judge if it is actually valuable as long as one doesn't have a previous education. The only exceptional and novel belief (prediction) on here is that regarding the risks posed by AGI.

Obviously you cannot form a good judgment as to whether a person is a good rationalist by determining whether his opinion on a difficult subject matches your opinion. And, even more obviously, you can't do so based on Anna's authority.

Instead, you need to interact with the person on an issue of intermediate difficulty and notice whether what he says clears cobwebs from your mind and shines light in dark corners. Or whether you come away from the conversation more confused and in the dark than before.

You may notice that I am implicitly defining rationalism in terms of how well a person communicates rather than how well they think. And even more than that, I am focusing on how well he communicates with you, rather than how well he communicates in general. If you wish, you can object, saying "That is not rationalism". Well, perhaps not. But it is the characteristic you should seek out in your interlocutors.