Comment by Brian_K_White

But a writer may use the construct for style reasons. ex: "Vaster than empires, and more slow."

I think it's just not actually technically wrong in the first place, merely uncommon because it's a little awkward.

What makes it ok is it can be used deliberately to build imagery or to intentionally trigger thought because you have to stop to parse it.

What makes it "wrong" is exactly that having to stop to parse it. It's obfuscated meaning to say "increase the decrease". A decrease is a property that may be increased, so it's legal, but you have to stop to puzzle it out rather than know what it means instantly without thought.