** If you want a Lisp file to be read in unibyte mode,
use -*-unibyte: t;-*- on its first line. That will force Emacs to read that file in unibyte mode. Otherwise, the file will be loaded and byte-compiled in multibyte mode.

Thus, each lisp file is read in a consistent way regardless of whether you started Emacs with --unibyte, so that a Lisp program gives consistent results regardless of how Emacs was started.