2.1.263 Part 1 Section 17.8.3.2, charset (Character Set Supported By Font)

a.   The standard states that when a font is unavailable the charset element shall not be modified.

Word can modify the charset element of an unavailable font if a font with the same name has been loaded before in the same Word instance.

b.   The standard specifies that the characterSet attribute is a valid attribute of the charset element.

Word ignores the characterSet attribute.