Interconnects, some have directional indicators, why?

Atmosphere's quote above perfectly explains how directional wiring would hurt the sound. The current is alternating back and forth, not flowing downstream. His diode analogy is spot on: if the current flows better in one direction, it is restricted in the other; therefore, directional wiring will absolutely make the sound worse. The argument that just grounding one end sounds reasonable... or would, if anyone would explain why the grounded end hooks to the source, rather than the input of the amp or preamp. Of course, no one has mentioned this.

+danvignau The shield should be connected only at the source end so that any interference that is picked up by it is reverted to the source and not transferred to the input device. This lowers the susceptibility to interference from electromagnetic signals in the surrounding and therefore improves the signal integrity. One exception is microphones where the shield should be connected at both ends so that the casing of the mic is grounded. The same applies to turntables/tone arms and battery operated equipment if no separate ground connection is used.

The shield can thus be considered as an extension of the source units cabinet.

And now we have claims of photons travelling down pieces of copper.  I guess that would be responsible for creating a truly holographic imaging experience.  No wonder this topic always sparks controversy.