Knowledgeable PO replaced front pads and caliper bolts in 2015 and in 2016 he rebuilt the rear brakes, new Brembo drums, shoes, wheel cylinders (tii versions), rubber hoses, parking brake cables. That of course doesn't rule out that the leak is somewhere there. I think it's actually more likely, since my reservoir fill level was dropped way below the clutch feeder line and into the two separate brake compartments at the bottom. If the leak was in the clutch and not the brakes, wouldn't it have stopped dropping further down once the clutch feeder line lay bare?