Most customers do not know that the tip they leave for the waitress is going to be split, the exception being the busboy and bartender. They leave a tip according to their service and food. While I DO voluntarily tip the kitchen on exceptionally good nights or when a particular customer asks me to, it's not a regular occurrence. Let me point out, the kitchen is not taxed on tips, the waitstaff are. I suppose if we were all working at a very upscale establishment and our tips ex ceded the norm, we could afford to tip the kitchen.
Every restaurant is different.
However, there are servers out there who are exceptional. She was a comedian with the customers. Because Natasha was serving them. They commented that they could have been served cornflakes and it would not matter because she brought them such exceptional service. So, I followed her one night to see what she does to make the customers so happy and how the other servers can learn.