Myelin

Myelin is reducing signal loss, induction of the activation of the axon can move further before it has to be recharged, the wavefront therefore moves faster. How myelin reduces signal loss is either by insulating (increasing resistance peripherally), or, by acting as a conductor (decreasing resistance, imitating how larger diameter axons have lower signal loss. )

The context I see where it makes sense that myelin is an insulator, is if there is anything to insulate against. This has, in my opinion, always been explained very loosely. I can see one simple way myelin has to insulate the current and that is that there is an actual current of electrons, that originates from a store of electric potential in a way analogous to a battery. This store could be Ca2+ ions in reduced form, stored within the endoplasmic reticulum throughout the axon, that when released function equivalent to Zn2+ ions in the anode of a galvanic battery.