It doesn’t matter what aspect of power you’re measuring, please provide the measurement of the effect it has, as you claimed!
To actually proof the fact that this kind of "leakage" does something, someone would probably need to build a contraption where he can actually influence the leakage directly to a larger degree, maybe then things become "obvious", also a proper measurement device probably helps here...
beside that, i have active speakers and a usb powered interface currently, so measuring this in any form is pretty much impossible with my current setup, unless i do it the multimeter way
I just measured the Ifi Power X 5V power supply.... if its turned right around i measure 0,02V leakage .... on the other (wrong) position i measure 0,25V .... thats a factor of 12.5
Also measuring on a 5V power supply in relationship to the actual ground 0,25V leakage seems actually quite high
If these things are not enough to show you there is a actual difference i dont know what will, but i guess you wanna see some dac output measurements
well for me, i just turn the friggin plugs the right way for free and stop wondering about this crap since measurements line up with audible preference here... (but i know, this is the wrong sentence in this forum....)