I think LessWrong as a whole would find you less frustrating if you assumed most comments from established users on domain-specific concepts or facts were more likely to be correct

Agreed. That's easier. However, sometimes the easier way is not the correct way.

In a world where the authoritative "facts" can be wrong more often than they're right, scientists often take a roughly superstitious approach to science and the educational system isn't even optimized for the purpose of educating what reason do I have to believe that any authority figure or expert or established user is more likely to be correct?

I wish I could trust other's information. I have wished that my entire life. It is frequently exhausting and damn hard to question this much of what people say. But I want to be correct, not merely pleasant, and that's life.

Eliezer intended for us to question authority. I'd have done it anyway because I started doing that ages ago. But he said in no uncertain terms that this is what he wants:

In Two More Things to Unlearn from School he warns his readers that "It may be dangerous to present people with a giant mass of authoritative knowledge, especially if it is actually true. It may damage their skepticism."

In Cached Thoughts he tells you to question what HE says. "Now that you've read this blog post, the next time you hear someone unhesitatingly repeating a meme you think is silly or false, you'll think, "Cached thoughts." My belief is now there in your mind, waiting to complete the pattern. But is it true? Don't let your mind complete the pattern! Think!"

Perhaps there is a way to be more pleasant while still questioning everything. If you can think of something, I will consider it.