Having worked in the restaurant business, I am always sensitive to tipping waiters / waitresses appropriately - i.e. always at least 20%, even for subpar service, unless my experience was just all-around flat-out horrible, because I don't want to screw over the host / barstaff / porters / etc.
So my question is - what should you do if the person you are dining with tips unfairly? There are different factors at play, for example when we split the bill and my companion says they are tipping lower due to x or y factor, I usually surreptitiously make up the difference on my own tip.
But how about when your companion picks up the entire bill? For instance: The other night I was out with a friend visitng from out of town. I took him to one of my favorite restaurants in the city, where I am a regular, and am on a first-name basis with most of the staff (both front + back of house). After our meal he offered to pick the entire bill. I protested; he insisted; so I thanked him and offered to get the next one.
Then he made some comment about mentally doing the math for a 12% tip. I would've thought that was low even for barely-acceptable service, but, per usual for this particular restaurant, the service we had had that evening was absolutely splendid - they sent out plates and desserts on the house; the bar sent over cocktails; the chef came out to greet us after our meal.
I felt particularly crappy about it because this was sorta like, "my place", you know? When I come here I usually tip well above 20% (to make up for some of the food they always send over gratis). I thought about slipping the waiter some cash on our way out the door but didn't have an opportunity to do it in a way that my companion wouldn't witness.
What would you have done? Tip more the next time you go? Apologize to the waitstaff later? Asked your companion to leave a higher tip?? I didn't want to make him feel like a cheapskate or insult him after he so graciously paid for my meal. Gah.