Related to: Why Our Kind Can't Cooperate
Eliezer described a scene that's familiar to all of us:
Imagine that you're at a conference, and the speaker gives a 30-minute talk. Afterward, people line up at the microphones for questions. The first questioner objects to the graph used in slide 14 using a logarithmic scale; he quotes Tufte on The Visual Display of Quantitative Information. The second questioner disputes a claim made in slide 3. The third questioner suggests an alternative hypothesis that seems to explain the same data...
An outsider might conclude that this presentation went poorly, because all of the people who spoke afterwards seemed to disagree. Someone who had been to a few conferences would understand that this is normal; only the people who disagree speak up, while the the rest stay silent, because taking the mic to say "me too!" isn't a productive use of everyone's time. If you polled the audience, you might expect to find a few vocal dissenters against a silent majority. This is not what you would find.
Consider this situation more closely. A series of people step up, and say things which sound like disagreement. But do they really disagree? The first questioner is only quibbling with a bit of the presentation; he hasn't actually disagreed with the main point. The second questioner has challenged one of the claims from the presentation, but ignored the rest. The third questioner has proposed an alternative hypothesis which might be true, but that doesn't mean the alternative hypothesis is true, or even that the questioner thinks it's likely. If you stopped and asked these questioners whether they agreed with the main thrust of the presentation, they would probably say that they do. Why, then, does it sound like everyone disagrees?
In our community, we hold writing and arguments to a high standard, so when we see something that's imperfect, we speak up. Posting merely to indicate agreement ("me too") is strongly discouraged. In practice, this often translates into nit-picking: pointing out minor issues in reasoning or presentation that are easy to fix. We have lots of practice nit-picking, because we do it all the time with our own writings. We remove or rework weak arguments, expand on points that need clarification and tweak explanations with every draft. Revising a draft, however, does not mean questioning its premise; usually, by the time the first draft is finished, your mind is set, so the fact that you agree with your own paper is a given. When reviewing someone else's work, we transfer this skill, and something strange happens. If we agree, we want to help the author make it stronger, so we treat it as though we were revising our own draft, point out the sections which are weak, and explain why. If we disagree, we want to change the author's mind, so we point out the sections which caused us to disagree, and explain why. These two cases are hard to distinguish, and we usually forget to say which we're doing.
Discussions on the internet are usually dominated by dissent. Conventional wisdom states that this is because critics speak louder, but I think this is amplified by posts that are meant to be supportive but sound too much like dissent. In order to combat this, I propose the following social norm:
When criticizing something in a post other than the main point, authors should explicitly state whether they agree, disagree, or are unsure of the post as a whole.
Imagine the same conference as earlier, except that each questioner starts by saying whether or not he agreed with the presentation. "I agree with your conclusion. That said, the graph on slide 14 shouldn't use a logarithmic scale." "I agree with most of what you said, but there's a claim on slide 3 I disagree with." "I'm not sure whether I agree with your conclusion, because there's an alternative hypothesis that could explain the data." The content of these responses is the same, but the overall impression generated is very different; before, it seemed like everyone disagreed, but now it sounds like there's a consensus and they're resolving details. Since the impression people got of speakers' positions disagreed with what they would have said their positions were, that impression was false. That which can be destroyed by the truth, should be; therefore, if enforcing this rule really does change the tone of discussions, then rationalists should enforce it by asking people to clarify their positions.
I agree with most of your analysis, but, if we're going to be expressing agreement more often in random discussions, we should seriously consider devices for reducing information cascade. We may need speech signals that distinguish between "I have independent evidence that should add to our confidence in the speaker's conclusion" and "based on the evidence others have presented, I now agree, but don't take my agreement as further reason to update".
Meta: It would be nice if people did this when they were commenting or upvoting/downvoting
edit: just realised you're basically identifying the synthetic/analytic divide, discussed heavily in analytical philosophy. Quinean critiques apply, I don't see a distinction between those two and therefore don't see a need to signal this sort of thing.