That seems an odd choice indeed, because even if you do have different normalizations in differnet parts of the system, you don't need to keep multiple copies -- you just need to apply the right normalization in the right place. All of the unicode normalization algorithms are both idempotent and of course completely deterministic. If you apply NFD to any legal input, you get the same thing every time -- there's no need to store the NFC version separately to compare it to NFC input when all you have is NFD otherwise, you can just normalize the input to NFD to compare it to what you have!

Unless it was meant to be for performance?