Well, CodeHelpers::stringLiteral is the wrong function to use because it inserts C++ code like "CharPointer_UTF8", but using CodeHelpers::addEscapeChars might do the trick?
Well, as long as the file is UTF8 and your text editor is doing its job properly, then everything should work just fine. And TBH when you're editing these files you probably do want to actually see the extended characters rather than some escaped sequences. It's not like working on a source-file where you need to ensure the compiler gets it right.