And? Due to power-law distribution that 0.1 % holds disproportional amount of riches.

I really don’t get that people talk about rising income inequality all the time, but actually noticing it (i.e. very strong minority holding many assets) suddenly doesn’t make sense.

No one is denying that income and wealth are distributed very unequally. But my point is that well more than 99.9% of individuals primarily earn money via labor and are therefore subject to an income tax, and so it isn't correct to assert that income taxes don't hurt the rich. They don't hurt the absolute richest individuals - but most people aren't defining "the rich" as only the top 0.05%.

Then I’d like to hear alternative definition of rich and see whether it is sound.

"Rich" is an ambiguous term; there clearly isn't a single definition. That being said, I think most people would agree that an individual who earns a salary of $500k a year (~99th percentile in the United States) is clearly "rich."

The question I'd put back to you is why it's useful to have a single, universally agreed-upon definition of "rich"?