[galangalalgol]

Does it matter that the tip is given after the service insteaf of before? My kids yoga teacher has a "pay what you can or what it is worth to you" scale so disadvantaged kids can come. I think of tips kind of like that.

[iso1631]

No, it's both again induce (i.e before) and reward (i.e. after)

It comes down to the definition of "improper".