The main issue is that it adds validation code (if one is sticking to the standard) for things that don't care about UTF-16 at all.
It does occupy 1/32 of the BMP, displaying a couple thousand potential actual characters (making them take an extra byte in UTF-8, and an extra two in UTF-16).
It does occupy 1/32 of the BMP, displaying a couple thousand potential actual characters (making them take an extra byte in UTF-8, and an extra two in UTF-16).