As an expert sommelier and brewer, I have encountered many situations where gratuity is included in the check. The general rule is that if gratuity is already included, you technically do not need to tip extra. However, this doesn't mean that you can't if you want to show appreciation for exceptional service.
In my personal experience, I have often found myself in situations where I wanted to add a little extra to the tip, even if the gratuity was already included. This usually happened when the service was exceptional and went above and beyond my expectations. For example, if the server was particularly knowledgeable about the menu and provided excellent wine recommendations to pair with my meal, I would feel inclined to leave an additional tip as a gesture of gratitude.
On the other hand, if the service was subpar or lacking in some way, I would not feel obligated to leave an additional tip on top of the included gratuity. It is important to note that the gratuity is there to cover the standard service provided, and it is not expected for customers to add more unless they feel the need to do so.
One situation where I may consider adding more to the tip is if my group was particularly demanding or complicated. For instance, if we had a large party with specific dietary restrictions or multiple special requests, I would understand the extra effort required from the server and may choose to leave a little extra as a token of appreciation for their patience and attentiveness.
However, I want to emphasize that tipping on top of a 20% gratuity is not expected or mandatory. It is ultimately up to the individual's discretion and personal assessment of the service received. If you feel that the included gratuity adequately reflects the service provided, there is no need to add more.
While gratuity is included in the check, it is not uncommon to tip extra for exceptional service. This is entirely optional and based on personal discretion. If you feel that the service went above and beyond, adding a little extra can be a nice gesture, but it is not expected.