You have to always decode. Note that Unicode is a list of integers with a meaning. iso-8859-1 is an encoding (of a subset of Unicode). UTF-8 is also an encoding. UTF-16 is another. It just happens that for the first 128 code points, the encoding in iso-8859-1 and UTF-8 are identical. But that wasn't part of Juerds claim.
in reply to Re^6: How to reverse a (Unicode) string
in thread How to reverse a (Unicode) string