The controversial: Some folks claim that longer power cables can result in better SQ. The explanation typically offered attributes the improvement to reduced "reflections." That may be nonsense
It is nonsense for audio cables. I'm not sure about power cables but home wiring is so long that any difference shouldn't matter. I don't know why longer cable should reduce reflections and if it does it wouldn't be a good thing, since we're talking about high frequency energy, that is far better to dissipate in cable on multiple reflections than to enter power supply.
The system specific: On a few occasions I've had cables that were so short that they created a "nest" of criss-crossing behind components. In those cases, I have sometimes opted for a longer cable to provide wider spacing between cables, which at least in theory, could result in less interference and therefore better SQ.
True, but I'm only talking about "sound" of the cable alone. Speaker wires 1ft long will most likely sound better than 10 footers but speakers 2 feet apart will not. Longer IC might allow to separate interacting components benefiting overall sound but it doesn't change the fact that shorter IC causes less of transparency loss itself.
The semantic: The generalization that "Shorter cables are always better" might give a false impression that shorter cables are always AUDIBLY better than longer ones of otherwise equivalent design. I suspect that, for any specific design, there is a range of lengths which are sonically indistinguishable.
True, but if you believe that particular cable has any affect on the sound then half of the cable will have half of the effect.