Anyone notice on an aftermarket rotor that the contact point that touches the cap points may or may not have a tape covering? Some rotors do and some dont. Is this to prevent arcing?

 

I believe the tape you're referring to is composite electrical insulator board. Basicly unprinted, unmasked circuit board. It is indeed there to decrease the chance of arcing. Rotors without it can have a thin insulating coating on the sides of the terminal that isn't always apparent to the naked eye, so not having the board doesn't necessarily mean there's no insulation. Honda distributors are designed well enough not to require the boards.