Right, command substitution. In my opinion, it's unfortunate that
command substitution in zsh splits on IFS by default. I wish this
wasn't the case. It's not even common that one wants to split command
output into words. Lines -- perhaps, but not words. So the default
behavior in this case is rarely what is desired and has to be actively
turned off.
What are the vectors? First must be logical necessity, second
consistency -- avoid strange exceptions -- third and fourth would be
helpfulness and tradition, with old-school guys favoring tradition
and guys like me favoring helpfulness. I've spent more hours trying
to get splitting issues correct than anything else. Characters,
words, IFS, lines, elements ... it's the most obscure and confusing
part of the shell. Lacking any focused explanation of the entire
subject what I do is just throw saved snippets of code at problems
until something sticks -- it looks about right, but even there I
might think I have line splitting when it's really elements. I wish
there were enough of us on this list to put things to a vote
sometimes and in this case I'd bet that Roman's view would win
overwhelmingly. I myself almost always want lines. Or elements.
Sometimes words, almost never characters.