I understood it, though if you're in regular contact, maybe I only think I do.

Essentially, the belief that to be definable is to exist leads to moral nihilism, much as some thing Many-Worlds does ( no matter what you do, it'll still be undone in other worlds. Each 'good' world as an equal and opposite 'bad' world).

The second half I understand the sentences of, but don't think Metafire has provided enough details here. Certainly, I don't see how some kind of weighted function over all ethical systems or volitions could help expand their scope.