That goes well with common sense, but how would you go about giving it predictive value?
Well, the first approach that comes to mind would be looking for some actual metric of status... preferably one that doesn't interrupt the conversation. My guess would be that how often a person is interrupted vs. allowed to finish a statement, patterns of eye contact, and participants' physical orientation relative to one another, and other indicators of attention are all correlates of status of the kind we're talking about here. (This is, of course, only useful for determining relative status of individuals within a conversation, and possibly within a culture; different cultures reflect status differently.)
Then measure it, and look for speech patterns that correlate with it. Anthropologists (and in a sense, ethologists) do this sort of thing all the time.
Certainly from a evo psych theoretical standpoint, it's odd to gain status by talking about how unhealthy and unfit you are.
Well, if low-status players all start talking themselves up as a way of gaining status, they create a context where someone can ostentatiously refuse to talk themselves up as a way of signaling that they are too high-status to care, which in turn creates a context where someone can ostentatiously talk themselves down as a way of one-upping that. If something like this is going on, then it's possible that talking about how unfit I am becomes a way of signaling how fit I am.
OTOH, talking about how unhealthy I am can also be a form of malingering, which has certain immediate practical benefits. That is, it might not be an evolved trait at all, and its prevalence in a particular culture might just be historically contingent.
One way of teasing this apart would be to see, in communities that do this sort of status-jockeying, whether the people who most claim illness are in fact perceived as ill by their peers.
Communication fails when the participants in a conversation aren't talking about the same thing. This can be something as subtle as having slightly differing mappings of verbal space to conceptual space, or it can be a question of being on entirely different levels of conversation. There are at least four such levels: the level of facts, the level of status, the level of values, and the level of socialization. I suspect that many people with rationalist tendencies tend to operate primarily on the fact level and assume others to be doing so as well, which might lead to plenty of frustration.
The level of facts. This is the most straightforward one. When everyone is operating on the level of facts, they are detachedly trying to discover the truth about a certain subject. Pretty much nothing else than the facts matter.
The level of status. Probably the best way of explaining what happens when everyone is operating on the level of status is the following passage, originally found in Keith Johnstone's Impro:
The level of values. Here the participants of a discussion are primarily attempting to signal their values. Any statements that on the surface refer to facts actually refer to values. For instance, "men and women are equally intelligent" might actually mean "men and women should be given equal treatment" while "there are differences in the intelligence of men and women" is taken to mean "it's justified to treat men and women unequally".
The level of socialization, also known as small talk. You aren't really talking about anything, but instead just enjoying the other's company. If the group is seeking to mainly operate on this level, someone trying to operate on the level of facts might get slapped down for perceived aggression if they insist on getting things factually correct.
For rationalists to succeed in spreading our ideas, we need to learn to recognize which level of conversation the discussion is operating on. One person acting on the level of facts and another on the level of values is a conversation that's certain to go nowhere. Also, it took me a while to realize that there have been occasions on which I was consciously trying to act on the level of facts, but my subconscious was operating on the level of status and got very defensive whenever my facts were challenged.
Usually what rationalists would want to do is to move the conversation to the level of facts. Unfortunately, if a person is operating on the level of values, they might perceive this as an underhanded attempt to undermine their values. I'm uncertain of what, exactly, would be the right approach in this kind of a situation. Defusing the level of status seems easier, as people will frequently find their unconscious jockeying for status silly once it's been brought to their conscious attention.