My problem: With my Emacs 26.1 on my 10.13.6 Mac, I have a opened a third-party text file, and it turns out I have the wrong encoding set : the text is in French , and the accentuated characters are displayed incorrectly (thus "é" is displayed as a brown
\216, "î" as a brown
What I tried : I tried
M-x revert-buffer-with-coding-system latin-1 and
M-x revert-buffer-with-coding-system utf-8 emacs
and nothing changed in the display.
I also tried (and failed) to guess the encoding : it must be an encoding in which "é" is the 216th character. Now é is U+00E9 in Unicode, which gives 233 in decimal. Also é is number 130 in extended ASCII.