I know this is an old thread, but I've just removed my E92 CDV today, and ended up with no fluid in the system after trying to bleed... The reservoir was up to the MAX mark, so I was mystified, and worried that I wouldn't be able to figure it out.
Eventually I noticed that the way the reservoir is partitioned for brake / clutch is bloody daft... There is a tiny tiny little partition at the back left (where the flexible woven reinforced pipe exits to clutch master). This is the only volume of fluid dedicated to clutch, and only flows in from the rest of the reservoir when it is absolutely brim full (way above the MAX line).
Hence it is very easy and not at all obvious that the reservoir can be at MAX level, but the clutch reserve is gone!!!!
After noticing this and keeping the reservoir absolutely full, I still couldn't satisfactorily bleed all the air out, and it's still a bit spongy but luckily drivable... After reading this thread, I'll be buying an oil can to try again...