I don't see this as an Argentine codigo. It's been my experience dancing in the New York City area in various post high school dance scenes that it's considered to be "gentlemanly behavior" to ask a guy with a lady if he minds if she is asked to dance. This is NOT asking his permission to dance with her, but acknowledging that he may be interrupting. If it's ok, the lady is then asked. It's her decision to dance or not. Also it may not be his wife SO or GF, it could be a friend or cousin or whatever, their relationship status can be unknown.
My sentiments exactly. To support your conclusion, tango is not only supposed to be '
refined' (better than the way people conduct themselves in other dance styles), but it's a time-honored tradition where men are supposed to be masculine (and respected by other men), and women are supposed to be feminine and treated as ladies (and respected by men as well).
Which means, at a minimum, a man should get an acknowledgement from another man that he'd like his approval to ask for a dance with the lady he considers his partner. A couple may be sitting-out a tanda (or two) waiting for the right moment, just enjoying the music, or watching other dancers.
This isn't the wild '
club scene' where anything goes, at least that's what I thought, nor is it Tarzan and Jane stuff either.
That said, I also believe it's good practice for a woman to get an acknowledgement from another woman if it's "okay" to dance with their man (BF, spouse, dance partner, etc.).
Etiquette like this is not only good for the community and a 'social grace', but for the individual dancers as well, especially couples and partners (and their relationship with each other).
Chapter 4 Near the Tables - 'The Couple':
Tango for psychological wellbeing. The blog explores dance as a primal part of our humanity, as seen by children dancing naturally. Have we forgotten?
tango-therapist.blogspot.com
"The general rule of thumb is that when you approach any couple you will need to engage both in this agreement."