

/usr/bin/true and /usr/bin/false come to mind.
Then there’s /usr/bin/test, or more commonly known as [
.
How about function fn { return 1; }; fn
?
POSIX-like shells consider that a failure, doing that on Bash with set -e
or on Zsh with setopt err_exit
will close the shell.
Should I compile a list of examples with common utility programs like mkdir
, or should I investigate whether 0-is-success also applies to PowerShell-run programs on Windows (idk for sure)?
Spaces behave like this because markdown was designed to be like HTML but quicker to write and easier to read without formatting;
most web services that use markdown translate it to HTML rather than parsing it directly, and in HTML whitespaces are supposed to work like you demonstrated in your comment.
The reason for this behavior in HTML is “because someone in the 90s said so”, I’m afraid.