In this section:
Multibyte characters in identifiers (6.4.2)
Additional multibyte characters may appear in identifiers depending on the chosen encoding for the source file. The supported multibyte characters must be translatable to one Universal Character Name (UCN).
Significant characters in identifiers (5.2.4.1, 6.4.2)
The number of significant initial characters in an identifier with or without external linkage is guaranteed to be no less than 200.