The Comfort Layer is the uppermost layer (or layers) on a mattress and is typically comprised of latex foams, poly foams, and/or wool. It's the layer that directly cradles you as you sleep.
A DIY mattress support layer is the base layer of your mattress and is usually a pocketed coil system, a firmer slab of foam, or a stuffed wool (or other fiber) mat.
Adding luxurious extras to your DIY mattress creates not only a more relaxing sleep surface but also elevates your overall sleep experience. Your bed is your nest. Go ahead and feather it.