There was a Russian girl I visited a few years ago, she had a boyfriend who didn't know what she did. He thought he was dropping her off at a friend's apartment when in fact it was actually her incall location. I didn't know that, but happened to be early one day for our appointment and bumped into her getting out of his car. I ignored her, as she did me and returned after he left. Another time I saw her at the Eaton Centre with a guy, possibly the same or different BF and again ignored her. I asked her afterward if she had been worried I might speak to her and she said that she knew I was too intelligent to do something that stupid!
Yet again I saw her in Yorkville while I was with my then GF, I had no qualms as I knew she wouldn't approach me. Another time, she was driving on King St. and had stopped at a light. I looked at her, alone in the car, but she did not acknowledge me. I continued as if I didn't know her. Later she admitted to seeing me but was concerned that friends in the area would see her talking to a "stranger".
Discretion is of the utmost importance, you never know how the smallest action by you could affect someone else, better to be safe than sorry afterwards!
Another time, I was with a different GF and as we walked across an intersection, there was an Asian attendant I know from a nearby MP waiting in her car for the light to change. She remained expressionless, and as we passed her I looked behind and she gave a very discreet little half wave.
Discretion works both ways.
I have seen many MPas and SPs I know or recognize on the street and do not approach them unless they acknowledge me first. Why risk ruining a good thing when discretion costs nothing.