If someone clicks to give you a thumb you get a system message about it.
But then they can revoke the thumb by clicking again. But you don't get a message when someone revokes a thumb (what a sad event!)
So then they see that they accidentally revoked the thumb, but they wanted you to have the thumb, so they click again to make sure you got it. And then, of course, you just got a thumb so you get a system message (again).
I suspect that the above is what is happening when you get multiple notifications on the same thumb. I'm not sure what the solution is...
