Not a chance would I tip any of the QR Lounge staff! They have been well trained to perform their jobs to the best of their abilities. When I come across a particularly outstanding staff member I get their name and write to customer service about the service they provided, along with the location, date, time and my own contact information and PC Number in case they want to do a follow up interview. The correspondence is kept on their employment file and can be referred to during employee reviews. I think that is a better approach, rather than conditioning them to use body language and uncomfortable timing pauses to suggest the customer tips them :/