Having been "in the business" for many years (I also have a nephew how owns one of the most highly rates restaurants in the city), I can tell you the "stories" about what the cook or kitchen will do to the food of "difficult" customers is JUST THAT... stories!
Everyone talks big, and says they would do this or that. As Mike said... any restaurant worth anything, view it as part of the business, and would never tolerate anyone taking action.
On ships, the wait staff always make a point of telling you that if something isn't satisfactory to let them know.
In a restaurant, if I didn't like the taste of something I ordered, I'd just push it to the side, and pay for it, and remember not to order it again.
On a ship, I'm invited to send it back and get something else, no questions asked.... and I have. In fact the good waiters will notice you not eating something you ordered and almost beg you to let them get you something else.