If one looks at the circuit / ring diagram for the power feed to the starter motor, in the manual, all the safety switches involved (ignition / clutch switch / cut-out switch / kick stand), none of these appear to have any form of spark quench protection. From this, I would be inclined to deduce that any form of serious arcing would be just bad luck. Agreed, some points are more heavy duty in construction than others, but arcing can take place at any point if switched slow enough. Bottom line, the ignition is designed to take the brunt of the arcing, so it stands to reason to use it... but then one could argue about the clutch switch.