I think it's just a common thing that nobody has managed to successfulyl crack yet - and if they have they're usually not sure what they did!
It must be down to a design fault in either the components used or the way they are positioned on the bike.
I had mine serviced a month or two back, and in the 12 mile ride home from TecMoto both the back brake had gone soft *and* the clutch fluid had started to go black.
Not that I'm bothered - I hardly use the back brake and, as Shazaam says, the clutch fluid going black doesn't make any difference.