I just lost part of my weekend because of this ... joker - zero width space. I just used some snippets from google groups and didn\'t recognize that there are doubled charac
Not sure what you meant, but you can permanently turn showing whitespaces on and off in Settings -> Editor -> General -> Appearance -> Show whitespaces
.
Also, you can set it for a current file only in View -> Active Editor -> Show WhiteSpaces
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Edit:
Had some free time since it looks like a popular issue, I had written a plugin to inspect the code for such abnormalities. It is called Zero Width Characters locator and you're welcome to give it a try.
A very simple solution is to search your file(s) for non-ascii characters using a regular expression. This will nicely highlight all the spots where they are found with a border.
Search for [^\x00-\x7F]
and check the box for Regex.
The result will look like this (in dark mode):