Well it looks like it depends what kind of therapist you are, I don’t see anything wrong in acknowledging a client, what’s wrong is to talk to others about their problems, that’s have been discussed in confidence, which you can’t really by law, I have no problems with acknowledging people, sometimes it’s part of their therapy?I would consider reporting any therapist that did any kind of affiliate link with a client to their registered body (bacp/ukcp etc)
It doesn't sit right ethically with me, but then I have an agreement with my clients that I won't even acknowledge them if I see them outside of our sessions unless they wish to acknowledge me, then it'll be a hello or nod etc, I'd not want it splashed all over social media...