5.9, running on macOS. zsh fires up with multibyte enabled by default, which is visible in the way it handles multibyte characters (e.g. x=ā; echo $#x shows 1). I can turn the option off, and the behavior changes (e.g. the same parameter has a length of 2). 

But `unsetopt` always shows `nomultibyte`, and `setopt` never shows `multibyte`, regardless of the actual setting.