The section you quoted does refer to the ASCII character set several times. However, the section on "MIF data items" defines a string to be "Left quotation mark ( ` ), zero or more standard ASCII characters (you can also include UTF-8 characters),
and a straight quotation mark ( ' )".
I wonder if the references to ASCII are leftover from an earlier version of the MIF reference, before FM supported Unicode. Stefan, do you remember when MIF switched to UTF-8? Was it in FM8 which introduced FM support, or in FM9?