I will on occasion tip in the CL. Usually I will give a $1 when I grab a couple of beers if they are free. A couple of times I have left a few dollars if the host did something above and beyond. However, I would be extremely unhappy with the OP hotel experience of being presented a receipt for the "meal" in the lounge. I mostly likely would "lose" the receipt and walk out without signing it. If I was chased down I guess Dewey Cheatem Howe would have to sign the slip :P