How to search and replace an unprintable character
You can try setting the encoding type and see if it fixes the visalizations of those characters:
:set encoding=utf-8
then you can use them directly. Alternatively, you can place your cursor on the unprintable character and hit ga, it will show the decimal/hex/octal code of that character, then you can substitute it with:
:%s/\%xYY/substitute/g
where YY is the hex code of the char, if it's multibyte:
:%s/\%uYYYY/substitute/g
for details:
:help character-classes
Note that you can search and match with \%xff or \%uabcd but will be unable to substitute with it.
I usually:
- delete the character with:
x - undo my change with:
u - do the substitute thanks to c_CTRL-R:
:%s/^R"/'/g