I think it's rather odd to do this, a little too exuberant/ borderline strange. But that's just me. This discussion pops up every once in while and I see that some people like doing this. I won't ever do this. I always try to be very polite and friendly. If I find the service exceptional, I write to UA commending her/him. That's pretty much it.

I don't support this unnecessary "tipping" mindset everywhere. Some of you are doing it with the expectation of getting personal recognition/ extra service from them. You know that deep inside your heart.