> You might just as productively argue that there is no such thing as a modern single-user system, since Windows isn't that either. His point is pretty clear.

Correct, and nonprivileged users can't install software globally on Windows either. Because it's now a modern OS, and that's how things are done. For very good reasons.

His point, as far as I can tell, amounts to: applications should be able to trash permissions on convenient directories and not have the OS complain or repair their damage.

Perhaps I'm being ungenerous here? I apologize if so.

On re read, I realize that tptacek is responding only to the SIP part of the discussion. OK, SIP is surprising to desktop computer users. But it's a good feature that requires a little adjustment to work with. But really not much, and none for the vast majority of users who don't muck with system directories.

He's arguing that users should be able to elevate their privileges by supplying root's credentials and then create a simple directory without having to reboot.

I more agree with you than with him, but his argument seems pretty straightforward.

Well, if you unwind far enough, I think the original discussion was about why Homebrew has trouble using /usr/local. Where "using" means "owning, adding git repos to, changing permissions on, etc".

OSX suggests /usr/local as a good location to install software, but insists that the directory itself be owned by root, and protects the parent directory /usr under SIP.

My assertion is that Homebrew is using /usr/local incorrectly (and in contravention to all expectation), and that blaming Apple for the problems thereby created is inappropriate.

I also think SIP is a good thing.