Adding that switch just sets your platform default encoding - that is,
any operation that involves an encoding where one hasn't been
specified will use the platform default encoding, which in your case
was probably ISO-8859-1.  That encoding didn't contain a mapping for
the character you are trying to output, so ? is used instead.  Now
that the platform default encoding is set to UTF-8, that does contain
a mapping for your characters and so the correct bytes are written to
disk.

Cheers,
Bryan Rasmussen