title: Highlighting and replacing non-printable unicode characters in Emacs
body: <p>I have an UTF-8 file containing some Unicode characters like LEFT-TO-RIGHT OVERRIDE (U+202D) which I want to remove from the file. In Emacs, they are hidden (which should be the correct behavior?) by default. How do I make such "exotic" unicode characters visible (while not changing display of "regular" unicode characters like german umlauts)? And how do I replace them afterwards (with <code>replace-string</code> for example. <code>C-X 8 Ret</code> does not work for isearch/<code>replace-string</code>).</p>
  
  <p>In Vim, its quite easy: These characters are displayed with their hex representation per default (is this a bug or missing feature?) and you can easily remove them with <code>:%s/\%u202d//g</code> for example. This should be possible with Emacs?</p>