Was Linus joking?
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. We understand perfectly well that much of it is just a matter of personal taste. He says, in so many words,
"Coding style is very personal, and I won't _force_ my views on anybody" -- at least outside of code he personally maintains. But consistency of style in a given project is a very good idea. I'd much rather code to a style I dislike than deal with multiple styles in a given function.
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)
body of function
Heretic people all over the world have claimed that this inconsistency
is ... well ... 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. I'm not going to grep the kernel source and count sequences of four tab characters, but I'd bet money you could find at least one that Torvalds wrote.
On the other hand, if somebody can write the Linux kernel without often exceeding three levels of indenting, a three-level limit might be an exercise worth trying out for a while in your own code, just to see where it takes you. This isn't like a sex change, you know. It's not a lifetime commitment.
If you run into somebody on the Internet who thinks he understands programming much better than Torvalds(2), well, you know what kind of people like to talk big on the Internet.
On the other hand, he is criminally wrong about eight-space tabs. That is the raving of a man who should be kept in restraints and fed through a slot. Four spaces is obviously correct.
(1) But note how he erroneously puts a space before the ellipses, and two spaces after them, and two spaces after a full stop. WRONG, WRONG, WRONG. And then he has the brazen gall to castigate heretics. The heretic is you, Torvalds! IT IS YOU!
(2) If you want to talk about "understanding how to design a source control system", there might be some room for debate.
Note: Dear fellow user who has repeatedly submitted the same edit: The formatting in the quoted material is kept exactly as the author meant for it to be. That's because it's from an essay about the formatting of fixed-width text, written in fixed width text, by somebody who has given the formatting of fixed width text a fair amount of thought. The formatting is a conscious and deliberate part of the author's intent, and it's relevant to the subject.
In addition, I referred back to that formatting in my own text. If you take out the pre-formatting, my footnote (1) becomes gibberish. If the pre-formatting is removed, so should be the text in my footnote (1) referring to the pairs of spaces after the full stops at the ends of sentences. I can see a rationale for removing that footnote anyway, on account of it being less funny than it seemed when I wrote it. But to remove the formatting without removing the footnote is unhelpful.