Can duct tape work for fading self harm scars?

NO! You cannot erase scars. Poor scars can be improved through the following methods: 1) scar massage 2) silicone sheeting (a kind of silicone tape you where over the scar) 3) steroid injections 4) laser treatment (helps remove coloring) 5) scar revision (removing the scar and starting over). Consult with a plastic surgeon to find out which combination of these would best work for you.