You can use other Unicode characters but only within comments and string literals.
Any Unicode character can be represented with an escape sequence composed only of characters in the lower 128 range. The escape sequence follows the normal tradition of specifying the character value (in hex) using its numeric position within the character set, like this:
Within a comment, such an escaped Unicode character is effectively ignored while within a string literal, it contributes a single character to the string.
Although all the characters in a conforming script are Unicode, they are treated with any context dependent interpretation as specified in the Unicode standard. The value of a 16 bit character is sometimes called a code point.