Thanks Martin for correction: yes not reserved - assigned.

Jean-Michel, you test case is incorrect. You terminal is run in CP1252
where byte \x80 is shown as euro sing. But if you run terminal(if is
possible in reported operating system) in ISO-8859-{1|15} this byte is a
control character without visual representation.

To avoid "visual" ambiguity you should use hex representation of characters:
1) >>> unicode('\x80', 'cp1252')
u'\u20ac'
2) >>> unicode('\xa4','iso-8859-15')
u'\u20ac'

For the second case in you terminal you should enter:
>>> unicode('¤','iso-8859-15')
u'\u20ac'
'¤'(cp1252) = \xa4 = 164 = '€'(iso-8859-15)

I guess you understand what is incorrect in you report.