> Am I adopting higher-status body language than them and they are keeping up?
You're playing a secondary game, countersignalling by conspicuously assuming a lower-status pose. You're both aware that you could instead assume their pose and play chicken with them about who will submit first. By "choosing the high road," you're saying that you've noticed the status game in play, and that now their implicit status move has become an explicit status move. And humans have strong norms about the group disapproving of explicit dominance. (See: democracy.) So when the person displaying the dominant behavior realizes they've been "found out", they stop.
Also,
> The feet on the table one, for example. To what extent is that signaling high-status simply because it's a very rude thing to do?
To answer this, consider the converse: to what extent could the fact that it's a rude thing to do be explained by anything other than it being a show of dominance?
In the case of picking one's nose, it can be considered rude because it is a private grooming behavior considered to be not especially hygenic by modern standards. It exposes bits of one's internal "grossness" to others. It would be uncouth even without dominance circuitry.
In the case of putting one's feet up on a table, though, I don't much see what could be wrong with it other than that it's a show of dominance. Perhaps we might be slightly wired to predict that feet are smelly or covered in dirt, but in the modern white-collar work environment this isn't the case--so it shouldn't be rude. And yet it is. So it's a dominance behavior.
(And in the case of scratching one's arse, I'm not quite sure--that doesn't seem dominant to me, but nor does it seem rude. It just seems like an artificial restriction created by some Tough environments[1] to stratify people by "those who can ignore all their bodily urges and pretend they don't exist for longest." This is called etiquette, and is a whole different kind of mating-fitness-signalling--more like birdsong than apes beating one-another up.)
The feet on the table did occur to me as one which I could have the wrong way around and while only "slightly wired to predict that feet are smelly or covered in dirt" may be true (seems unintuitive to me though), I think the perceived discrepancy is cultural as much as anything. I've noticed the ickyness of putting feet on tables is almost universally invisible to Americans, while in Japan it would seem completely unacceptable along with a whole host of other related customs, for example, the taking off of shoes and the special slippers to wear when you use the bathroom. Japanese ask me extensively about UK customs regarding shoes and feet, it's evidently considered a hygiene issue, much like their showering before bathing. In the UK the foot thing is probably a bit of both, varying from person to person, family to family. I was brought up such that I wouldn't ever consider putting my feet up on a table, even when completely alone in my own house. Our trains have signs telling you not to rest your feet on seats, I wonder if US trains do. What you say actually now reduces the offense that I would take if an American put their feet up in front of me. I would think "well for them this isn't considered gross, just a sign of relaxation that at worst is dominance behaviour" and I'd attempt to force myself not to be disgusted by it.
One other thing might be that outhouses were an American innovation[1], imported to other parts of the world later; and thus, of all rural-living subcultures (which are the usual source for a culture's hygenic mores/superstitions, being the most affected by them), rural Americans have had the longest to adapt to not worrying about getting shite on their feet. :)
You're playing a secondary game, countersignalling by conspicuously assuming a lower-status pose. You're both aware that you could instead assume their pose and play chicken with them about who will submit first. By "choosing the high road," you're saying that you've noticed the status game in play, and that now their implicit status move has become an explicit status move. And humans have strong norms about the group disapproving of explicit dominance. (See: democracy.) So when the person displaying the dominant behavior realizes they've been "found out", they stop.
Also,
> The feet on the table one, for example. To what extent is that signaling high-status simply because it's a very rude thing to do?
To answer this, consider the converse: to what extent could the fact that it's a rude thing to do be explained by anything other than it being a show of dominance?
In the case of picking one's nose, it can be considered rude because it is a private grooming behavior considered to be not especially hygenic by modern standards. It exposes bits of one's internal "grossness" to others. It would be uncouth even without dominance circuitry.
In the case of putting one's feet up on a table, though, I don't much see what could be wrong with it other than that it's a show of dominance. Perhaps we might be slightly wired to predict that feet are smelly or covered in dirt, but in the modern white-collar work environment this isn't the case--so it shouldn't be rude. And yet it is. So it's a dominance behavior.
(And in the case of scratching one's arse, I'm not quite sure--that doesn't seem dominant to me, but nor does it seem rude. It just seems like an artificial restriction created by some Tough environments[1] to stratify people by "those who can ignore all their bodily urges and pretend they don't exist for longest." This is called etiquette, and is a whole different kind of mating-fitness-signalling--more like birdsong than apes beating one-another up.)
[1] http://michaelochurch.wordpress.com/2013/02/20/1410/