Beginning with tango I was surprised to see some eligible tangueros (seldom tangueras) dancing with a bad looking posture. It took me some time to figure out, that this posture was a relict of "export tango", used by professional contemporary/modern dancers to gain flexibility to express best with her body, imitated by second level tango teachers, adopted by midfield tangueros that never had not much to express and many years of experience didn't change that. But with that experience they can embrace and lead quite well, additionally the can look onto their feet to make things easy. What I really want to say: people complaining about other peoples posture often target to the inner attitude of them. BTW: I was by no way concerned about their health - the main risk is to sit an office chair and not to dance.