Expert Answer:

Pat Nourse, Gourmet Traveller restaurant critic, writes:
"Tricky. Short of slipping a note over the pass into the kitchen on your way out or hiding it under a mound of uneaten cavolo nero, or having a face-off with your waiter, asking them to take the tip directly to the chef and not collect x-dollars themselves, you’ve got the choice of: (a) not tipping at all, aka the lose-lose strategy, telling yourself that the waiters are really the face of the kitchen and it’s their problem, or (b) tipping and hoping some fraction of your gratuity makes it back-of-house.

Tipping really is for service, though, and it’s the rare restaurant that kicks back tips all the way to the kitchen. I say take the scorched earth approach: regardless of your good intentions, tipping your bad waiter is rewarding poor performance, and that’s never a good policy. Stiff ‘em and, if you feel so moved, order the kitchen a nice bottle or some beers before you settle, slip some money to the maitre d’ for the kitchen on the way out, or send the chef a note of thanks and a gratuity in the post."