I think a better approach than doing away with the notion that obviousness is bad (because, to be honest, if something really is obvious to you, getting a detailed explanation of it can be very annoying), might simply be to explain concepts like inferential distances and mind projection to posters who don't seem to understand them. If people understand those problems of communication and others like them implicitly, they can more easily allow themselves to say something that might be obvious. At least it works that way for me. I won't explain seemingly obvious preconditions of a discussion unless called upon to do so, but I do my best not to assume that everything that might be obvious, is. There are usually plenty of clues. Even if it sometimes requires someone eventually saying "Uh, what does that mean?"
Maybe I'm being terribly optimistic. In my example of one, however, knowing that I have knowledge others might not share is usually enough to make me check if they understand me instead of making the supposition that they do.
Related to: Generalizing from One Example, Connecting Your Beliefs (a call for help), Beware the Unsurprised
The idea of this article is something I've talked about a couple of times in comments. It seems to require more attention.
As a general rule, what is obvious to some people may not be obvious to others. Is this obvious to you? Maybe it was. Maybe it wasn't, and you thought it was because of hindsight bias.
Imagine a substantive Less Wrong comment. It's insightful, polite, easy to understand, and otherwise good. Ideally, you upvote this comment. Now imagine the same comment, only with "obviously" in front. This shouldn't change much, but it does. This word seems to change the comment in multifarious bad ways that I'd rather not try to list.
Uncharitably, I might reduce this whole phenomenon to an example of a mind projection fallacy. The implicit deduction goes like this: "I found <concept> obvious. Thus, <concept> is inherently obvious." The problem is that obviousness, like probability, is in the mind.
The stigma of "obvious" ideas has another problem in preventing things from being said at all. I don't know how common this is, but I've actually been afraid of saying things that I thought were obvious, even though ignoring this fear and just posting has yet to result in a poorly-received comment. (That is, in fact, why I'm writing this.)
Even tautologies, which are always obvious in retrospect, can be hard to spot. How many of us would have explicitly realized the weak anthropic principle without Nick Bostrom's help?
And what about implications of beliefs you already hold? These should be obvious, and sometimes are, but our brains are notoriously bad at putting two and two together. Luke's example was not realizing that an intelligence explosion was imminent until he read the I.J. Good paragraph. I'm glad he provided that example, as it has saved me the trouble of making one.
This is not (to paraphrase Eliezer) a thunderbolt of insight. I bring it up because I propose a few community norms based on the idea:
I'm not sure if these are good ideas, but I think implementing them would decrease the volume of thoughts we cannot think and things we can't say.