No, sorry, I don't get it at all. Stop trying to read "signals" and get people's actual consent before touching them. It's not difficult or complicated.
Can you imagine the following scene:
"Gee John, you did a great job there, I would like to shake your hand, or even pat your back (only near the shoulder mind you and no lower than a line formed by the bottom of your shoulder blades). Do you think that would be permissible? I want to reassure you that this touch will not be sexual in any way."
As for patting backs, do avoid doing so. Many of us don't like it even if it's totally non-sexual.
...and many of us do like being patted on the back (non-condescending of course).
Perhaps in the future, we will all have to work in an environment where no touching of any sort is allowed, ever, but I can't help thinking that would be a step backwards.