Based on her likely experience with the previous ten groupon customers, you basically announced "I intend to tip you 25% of what you were expecting."

But rudeness in wait staff is a self-fulfilling prophecy. They treat you poorly so how can they expect a generous tip?

Yes, there's an element of self-fulfilling prophecy about it, but there's also acceptance of the inevitable. I know a few servers who I trust would remain professional and courteous to groupon customers. Universally complain that groupon users make poor customers. (Not strictly limited to groupon. "$2 specials everywhere" bar crawls of any ilk draw similar complaints.) I mean, it's not like all the servers got together and decided to A/B test groupon customers by being meaner to them than others just for the funsies. How does a server with no priors come to treat one group differently than another?

It's less self-fulfilling than you would expect. Research shows that tip amount isn't very affected by the quality of service, but much more affected by the person doing the tipping.

If you walk down a street and nine people punch you in the gut as they pass, it's a bit rich for the tenth person to complain that you flinched as they walked past. The wait staff are simply playing the odds.

I guess it's true that, had I tipped at all in that instance, I would have tipped based on what I paid on the night. Bearing in mind the Groupon was already paid for, that wouldn't have been a lot.

Having said that, I also went for a great Groupon meal somewhere else, which included a cocktail that was so good I had another 2, bought more food on top and ended up paying as much as a 'regular' meal would have been elsewhere (and tipped accordingly for the good service). That was the exception to the rule, though, even based on a very small sample size.

Based on it being Shoreditch, which is in London, the tip should have been 10%.

Do many people leave 2½% (essentially no) tip in London?

Nearly everyone tips based on the coupon value, not the market value. So that's maybe 50% less. They're also more "value minded" customers, who are likely to tip at the low end. Regular customers sometimes get the expensive bottle of wine; groupon users only ever get the cheapest bottle, if any. And then you get a subset of people who bring a $20 groupon and exactly $20 to the restaurant.

It doesn't mean everyone using groupon is automatically a jerk, but it definitely selects in that direction.

I naively thought that it's fair game that because I'm buying a £20 Groupon I might pay exactly £20. I never did, but I felt that it should be implied that that's acceptable. I certainly wouldn't have expected to be treated worse for it.

I think the expectations are not always in alignment, hence the friction. A simple solution would be for the groupon to say "$20, fixed menu, all tax and tip included." But you don't see a lot of that, although a lot of the advertising probably sounds like it. Your expectations aren't unreasonable, just... wrong. :)

> groupon users only ever get the cheapest bottle, if any.

Yeah, because absolutes like this help. Groupon customers can be just like any other customer out there. Some "regular" customers will get cheap wine, some will get an expensive bottle. Similarly, some Groupon customers will get the cheapest wine, others will take the money they saved by getting a Groupon and get the expensive wine. Being a "Groupon customer" might move the needle towards one direction but it's far from absolute the way you're making it out to be.

Many people tip on what they paid instead of the normal cost, so if they bought their Groupon at a heavy discount, they'll tip correspondingly less.