Is it possible for there to be such a thing as bad service which is not bad reviews?

The actual physical activities the restaurant does, such as choosing a menu, cooking food, handing food to customer, playing low music, cannot be good or bad on some independent scale. What you may see as bad service, I may see as great service.

I think the only possible thing is “what does the market think.” So the entire problem is correlation.

“Bad service” is, literally by definition, the name we give after the fact to types of service that correlated with bad reviews and low revenue.

> The actual physical activities the restaurant does, such as choosing a menu, cooking food, handing food to customer, playing low music, cannot be good or bad on some independent scale.

at a minimum, the health department disagrees, re cooking and delivering food.

I don’t see how health / sanitation law is related to the discussion.

Health/sanitation law is intended to stop people from getting sick from restaurant food. If you get sick from restaurant food, that would universally be considered a bad experience (and for those inclined, a bad review). That's a direct counterexample to the GP claim that there's no agreed-upon way to distinguish "bad" and "good" experiences.

I still fail to see why anyone thinks this is relevant. I agree health law exists for the purpose you cite - and this fact is not related to why patrons in the study give bad reviews of restaurants that are actively operating with permission of the health department.

> The actual physical activities the restaurant does, such as choosing a menu, cooking food, handing food to customer, playing low music, cannot be good or bad on some independent scale. What you may see as bad service, I may see as great service.

Once we went to a restaurant with hardly any diners, not at all busy. We ordered dinner. They served half our order. We waited for the other half. After about half an hour, we asked the manager. He went to investigate, and came back with the admission that they had forgotten to submit the other half of our order to the kitchen.

That's objectively bad service. I don't see how anyone could see that as "great service".

Now, maybe it was just an innocent mistake, someone having a bad day, and maybe the manager is really apologetic and offers some compensation and I forgive them. It would rule them out of consideration for a five star review, but I wouldn't give them one star just for that. Unless, if I had gone on a review site and saw a dozen other people complaining about the same restaurant messing up their order, then I probably would have left a one star review too.