I lied - it doesn't work either way when the attribute is href. It seems to 
  be fine when the attribute is not href doing it either way. I am using saxon 
  8. Here is my full stylesheet:


so in  that case it's down to 2 whether the % encoding happens before or
after the character mao (which will be specified in the serialisation
spec) you turn off %-encoding in xsl:output, as I mentioned.

david