The answer to that is that if you need more than 3 levels of indentation, you're screwed anyway, and should fix your program. Are there some things which absolutely need three or more levels of looping?
I think that similar guidelines would apply for any language when writing code that must be robust, security focused and auditable at the expense of other things. an encryption library written in Java or Haskell should also be written in a style that keeps things as simple as possible, limits nesting, and tries to separate everything into chunks that can be easily analyzed with all their possible [email protected] for example, machine learning code where you may want to use C just for performance reasons but don't care much about robustness or security since it will be run internally in controlled conditions.
Also, implementing simple business functionality on small embedded microcontrollers - in practice this often has a business like focus on features and development speed at the expense of quality and security, but uses low level languages..
Here's an example of clearly playful writing: However, there is one special case, namely functions: they have the opening brace at the beginning of the next line, thus: int function(int x) Heretic people all over the world have claimed that this inconsistency is ... inconsistent, but all right-thinking people know that (a) K&R are _right_ and (b) K&R are right.
Besides, functions are special anyway (you can't nest them in C). It's arguably good advice to try to keep indenting from getting out of control, though a three level maximum might be hyperbolic.
That is the raving of a man who should be kept in restraints and fed through a slot. (1) But note how he erroneously puts a space before the ellipses, and two spaces after them, and two spaces after a full stop. And then he has the brazen gall to castigate heretics.
(2) If you want to talk about "understanding how to design a source control system", there might be some room for debate.
The last sentence is only to underline that point, not to say that you must not use more levels of indentation - no rigidness implied.
The piece is written in a playful style which suggests that the author is familiar with the way coding style is discussed among serious practitioners: We all have our preferences, and we defend them rabidly, but with tongue at least partially in cheek.
It's about how you structure your code and keep it readable, maintainable and fun to modify for years to come.