I actually always use a pad in my hammock. I like the slight structure it provides.On a cot, I would just use a sleeping pad. Pads work poorly in hammocks, which is the reason for underquilts in them, they should be no issue on a cot.
I think he was talking about hanging a quilt under the sleeping surface so it would not compress, like a hammock underquilt.A quilt will compress under you giving less insulation- down especially. Syn quilt will do a little…but a waffle pad or two is more efficient.
I use a waffle matt and a foam pad on a cot since with a cot its a base camp so weight is not a factor.