Just remembered what Dale Carnegie wrote:

“A man convinced against his will,
Is of the same opinion still.”

Tipping 15% is being cheap.

......and over tippers are the "look at me" egotists.

15% is undertipping. I am not an egoist. I believe in providing a good tip for good service. The servers work very hard and deserve to be rewarded.

15% tip is more than fair.

Absolutely not. t is being cheap.

Who knows what one leaves, save for the recipient of the tip?

How is that "look at me"?

Exactly. The cheap tppers are always looking for an excuse to be cheap.

By their employer, not by their customers.

In order to do that they need to raise their prices, and the cheapskates will be screaming.

I put a stack of dollars bills on the table (estimating what the tip will be)

excellent service they get it all

I take a bill off of the stack for every mistake.

They get what is left

Bit like how the Rabbi and the Priest divied up the weekly collection.
The Priest said the Bishop gave him a percentage back for the church and his keep.
Rabbi said he puts it all on a plate, throws it in the air, God take what he needs, all that comes down is his.

Ask and you shall receive??

20% is easier for me to calculate but the process is the same.

I do get annoyed at the suggestion that 22%, 25%, or even 28% should be the new norm. In those cases I fight the urge to under-tip on general principles.

That is my point. It depends on the size of the bill. If it was under $20, they were being generous and if it was in the hundreds, they were being cheap.