John Gruber is the creator of Markdown.\
He describes the syntax here:\
https://daringfireball.net/projects/markdown/syntax

#### headers

https://daringfireball.net/projects/markdown/syntax#header

> Atx-style headers use 1-6 hash characters at the start \
of the line, corresponding to header levels 1-6.

=> that means header level 6 is the maximum level (vim and bat also do not highlight \
level 7 headings)

But there are also "Setext-style headers" that can only create \
level 1 and 2 headers.