My master has fantastic subdar. He spotted me out in a bar. Not that he was completely sure but he had a hunch. He's spotted a couple other people out as well. I on the other hand have no clue, even with couples. One couple I know turned out to be D/s. I was friends with them for 2 years and didn't know until they told me. I guess I'm just not as attuned, or don't pay good enough attention.