'Single' girls

A: I danced with a lovely dancer but he kept hold of my hands between tracks and conversation was personal questions not the music etc.

B: Single girls rarely allow that in a BA milonga

A was not single and B knew it.  It was no secret.  But if you arrive alone at a milonga in Buenos Aires, marital status doesn't necessarily count for much.  What matters when you arrive is how you appear.  

Perhaps my father guessed as much.  Maybe that is why he thought the milongas inappropriate for someone in your situation.  There were no hard feelings and the clarity was useful.

Much earlier:

B: I get a slight shock when you ID a dancer with full name. I don't expect people to know the second name of a dancer from a milonga. Where I come from :) it would be very rude to ask a partner's second name. Often old accounts of the milongas say people never knew anything about a guy except his given name, nickname and dancing. They did not know where he lived, what he did for a job (if he had one), whether he was married. All stuff gets left outside -- by agreement of all.

I guess nowadays, you know someone's name from his advertising. Or Facebook. Or is that the same thing? :)

At the time I found the warning over-egged - until I was asked just those sorts of questions.