Yeah that's what I was saying. Since KDSS is a closed loop (air should not enter and fluid should not escape) and it's under extreme pressure (600 psi, IIRC), at the point in time when you need to bleed the KDSS system you probably have other expensive issues with the system. If the KDSS system needs to be repressurized and bled, unless it's because you opened the screws too far, the cost of a new KDSS cylinder is just icing on the repair cake.It seems best to keep it from rusting in the first place, but you are taking a risk of causing problems in moving it at all, to keep a screw moving that really isn’t needed unless you need a major repair. At which point you’d probably just replace he whole valve body anyway.
Or at least that’s how I interpreted his comment.
It's worth coating in marine grease, but I wouldn't start trying to loosen it. It might be that it does nothing unless the KDSS valves are open, or it might be that 1/4 turn is enough to spray fluid everywhere.