Wow, a personal reply! I just doubt he's attracted to me from the neck up. That's not a self-esteem issue, it's just my well-honed sense. If he was a stranger I might hook up with him because our kinks kind of match, even though I'm not red-hot for him physically either. But if I expose my identity I'm afraid it would force him to come up with some way of saying, "Oh it's you, never mind then." — TMWAFP

You asked about the ethics of letting him know you know each other, TMWAFP, but as things stand you know him a little better than he knows you. But there are no ethical issues here. You no longer work together, you aren’t his boss, he's not your boss, etc. And while he might not be interested in meeting up to play, and while it's always awkward when someone bails after expressing interest, there’s a chance he might be interested. People into kink sometimes play with people they wouldn’t be into absent a shared interest in bondage or rubber or fisting or puppy play whatever the overlap here is. And while it's sometimes the case that one or both of those kinksters are focused on and/or exclusively turned on by the bondage or rubber, etc., sometimes learning a person you assumed was vanilla is actually kinky sparks a genuine attraction. Learning you're kinky could take you from a 3 to a 7 in his eyes. (You're slightly more attracted to him now that you know he's kinky than you were before, right?)

So send a face pic, TMWAFP, and say hello.

And you shouldn't worry about making things awkward, TMWAFP, because things are already awkward. You briefly worked together, you still work in the same neighborhood, you still see each other around but don't acknowledge each other. You walk past him you're thinking, "Oh, there he is, but he doesn't acknowledge me, so I won't acknowledge him," and there's a good chance he's thinking the exact same thing as he passes you. So to avoid the risk of momentarily losing face—the prospect of one of you saying hi and the other ignoring him—you're making your neighborhood feel unfriendlier and the world a little colder. Err on the side of making a connection, TMWAFP, by saying fucking hello on the kink app and in the street. Even if the worst should happen—even if he isn’t interested in playing—you could wind up bonding as friends over your shared interests. Even if it's a, “Never mind,” about the kinky sex, TMWAFP, it could still be a, “Want to hang out sometime?”, and that’s not nothing.

It’s good to have friends you can go to events and fetish nights with, TMWAFP, even if you never play with them. — Dan