from that first link you gave:
A small peaking capacitor mounted next to the plug can be added to a conventional ignition system as an aftermarket application. This will deliver more energy during the initial breakdown phase of the discharge and a larger spark formation. This increases ignition system performance for a small increase in cost.
At low load, however, when more potent ignition is needed to ignite the air/fuel mixture, the system shows little improvement, because it produces a low breakdown voltage. At high load, when enhanced ignition is not usually required, the capacitor is charged to high voltage and delivers significant unnecessary energy. In addition, the peaking capacitor causes rapid electrode wear, due to the high currents passing through a stationary arc.