Some rationalists have what to me feels like an obsession with honesty. That's fine: we can all be obsessed with our own concerns. But I also think it's a rather strange sort of obsession given the nature of truth and our relationship to it even if we assume the framing of Bayesian epistemology. This is a brief case that most thinking about honesty rests on shaky ground (and is therefore strictly incoherent) as presented and only makes sense through the lens of a generous, reconstructive reading.
Let's first be clear about what "honesty" means. The word "honesty" has its origins in "honor" and comes to have its relationship to truth telling by means of conflating together all moral virtues. I'm going to diverge from this history a use "honesty" as a technical term with a precise definition, and I do so because oddly in English have the single-word verb "to lie" but have to use a verb phrase to mean its antonym, "to tell the truth". This is unfortunate because "to lie" is the only word of the bunch that is not attempting to make a normative statement about the subject's actions or imply a disposition to either the action or the subject, but it would be an odd circumlocution to talk about antilying, so "honesty" it is.
(As we'll see, though, there's perhaps good reason for this: it's much easier to talk about what it means to lie than what it means to not lie!)
We might like to say a statement is honest if it is a true statement and to conflate honesty with truth as English tries to do, but this is to ignore that a person can be mistaken, and we would not call them a lier for stating what they believed to be the truth, i.e. they did not try to deceive. So instead we could say a statement is honest if it is a true statement about a person's knowledge, but this phrasing has two problems. First, it supposes that truth is a quality a statement can have rather than an assessment of some criteria someone makes about the statement; it would be safer to say that a statement is honest for a particular subject if they believe it to be a true statement about a person's knowledge. But perhaps you are an essentialist (you believe ontology precedes epistemology) and this is not a problem for you. No worries, because the second problem with this definition of honesty is that it still supposes we can reliably tell what is true contrary to epistemic circularity.
Since it's important, I'll elaborate. The problem of epistemic circularity is that to know something reliably something else must first be reliably known. It's core identification comes from the problem of the criterion, which observes that to know something reliably we must know the criteria by which things are reliably known, but to know the criteria by which things are reliably known is to know something reliably. It is tied to the problems of infinite regress and induction and creates an unreliable gap in our knowledge, positivists be damned, that prevents us from really knowing anything. I'll admit, this is mainly a philosophical problem because it has a pragmatic solution of just assuming some hinge propositions to be true and getting on with life anyway well enough to keep living, but it's worth knowing about because it is the source of uncertainty in all epistemology.
So if we want to talk about honesty in terms of truth we'll be hard pressed to do so in a coherent way because, while it does not necessarily require resolving the nature of truth, it does at least require resolving the question of assessing truth. Instead I think it makes sense to talk about honesty without appealing to truth, but then it turns into something rather weird: a statement about beliefs and beliefs about beliefs. Specifically, we might say a statement is honest if the subject making the statement believes the statement will lead listeners to believe the statement to be as likely to be true as the subject does. This makes honesty about beliefs rather than truth, and I think this is the undoing of much excitement about honesty.
The trouble is that beliefs, unlike reliable yet unobtainable knowledge of reality we might call truth or facts, are extremely unreliable in practice to the point that we often don't even know our own beliefs. This makes any thoroughgoing attempt to be "honest" doomed from the start because we can't even accurately assess the likelihoods we assign to our own beliefs let alone the beliefs of others. Even if we strive for something like Christiano's integrity we face serious issues of unreliability, and so I'm left wondering what this honesty business is even important for.
Obviously, virtue signaling. Making strong statements about honesty signals virtue and makes you appealing to ally with. But putting such extra-material reasons aside, I'm inclined to conclude that folks' interest in honesty is either due to their using "honesty" to mean something coherent but without defining terms or due to not fully updating on the fundamental unreliability of knowledge that epistemic circularity implies. I say this because I don't even know how to really trust my own beliefs, let alone the beliefs of others, but I don't view this as a problem to be solved so much as a reality to be lived with. Knowledge is unreliable, we will always be forced to reason unreliably, and concerns about honesty and truth distract from the real problem of better predicting future experiences (including experiences of learning about present and past events) and aligning those future experiences with ones values.
If you want to talk about coordination under uncertainty rather than honesty, that sounds much more interesting to me!