When I started Emacs with
I customized the variable "Bidi Paragraph Direction" to 1 (right to left)
It only affected this "Customize .." buffer and the bottom buffer. One of them is illustrated in the following picture:
Other buffers are left to right.
I tried this without
-q and it didn't work either after restarting Emacs.
emacs-version is GNU Emacs 25.2.2