Are there differences in mapping between UTS #46 and IDNA2003?
No. There are, however, 56 characters that are valid or mapped under IDNA2003, but are disallowed by UTS #46. For a detailed table of differences between UTS #46 and IDNA2008, see Section 8, IDNA Comparison in UTS #46. In particular, there are collections of characters that would have changed mapping according to NFKC_Casefold after Unicode 3.2, unless they were specifically excluded. All of these characters are extremely rare, and do not require any special handling. Case Pairs. These are characters that did not have corresponding lowercase characters in Unicode 3.2, but had lowercase characters added later. U+04C0 ( Ӏ ) CYRILLIC LETTER PALOCHKA U+10A0 ( Ⴀ ) GEORGIAN CAPITAL LETTER AN…U+10C5 ( Ⴥ ) GEORGIAN CAPITAL LETTER HOE U+2132 ( Ⅎ ) TURNED CAPITAL F U+2183 ( Ↄ ) ROMAN NUMERAL REVERSED ONE HUNDRED After Unicode 3.2, the Unicode Consortium has stabilized case folding, so that further examples will not occur in the future. That is, case pairs will be assigned in the same version of
