Ghosting is what we see when there are time-delayed copies of the image displayed (at weaker strength) alongside the original image.

These copies are reflections of the original signal from impedance mismatches in the cabling. Shorter cables will reduce apparent ghosting, simply because the ghost images don't have as far to travel as they bounce back and forth between the cable connections.

Gold plated contacts on all connectors will help to minimize impedance across the connections. The proper choice of correct impedence cable (by the manufacturers) can also help, as can cabling with better shielding. Ditto for the KVM switch itself -- better shielding there can help reduce pickup of stray emissions.

Cheers