To install this package, run in Emacs:
M-x package-install RET markchars RET
Mark special chars, by default nonascii, non-IDN chars, in modes where they may be confused with regular chars. See `markchars-mode' and `markchars-what'. There are two modes: confusable detection (where we look for mixed scripts within a word, without using the http://www.unicode.org/reports/tr39/ confusable tables) and pattern detection (where any regular expressions can be matched). The marked text will have the 'markchars property set to either 'confusable or 'pattern and the face set to either `markchars-face-confusable' or `markchars-face-pattern' respectively.