I wouldn't mind it personally, so long as it was something the employee could get without managers intefering/taking the money or it being mandatorily added to the end of the bill as a service charge. And it obviously shouldn't be necessarily to make up for a wage that the employee couldn't otherwise live on.
But there's nothing wrong with the idea of tipping per se, and if customers want to reward employees for good customer service/work, then they should be able to.
But there's nothing wrong with the idea of tipping per se, and if customers want to reward employees for good customer service/work, then they should be able to.