After the formatting is completed. The directory name will be
Directory (without ZWNJ): "ರಾಜ್ಕುಮಾರ್"
Directory (without ZWJ): "ರ್ಯಾಂಕ್"
Format function drops ZWNJ (u+200C) and ZWJ (u+200D). Both are invisible(non-printing) characters. Mac accepts them when I edit the folder directly. So, it is definitely the mp3tag, "format tag field" that is dropping the invisible(non-printing) characters.
This could be true for other invisible(non-printing) characters Non-breaking space NBSP U+00A0
I'm not sure yet, most users are not aware of those special characters and those of Unicode General Category Cc and Cf have caused a lot of hard-to-identify support issues in the past.
or At least is there a work around to this issue. I want to batch process folder names in unicode. It is possible they will have ZWJ, ZWNJ and I want to retain them