There's nothing that suggests electrons are a cloud. Yes, a "cloud" defines the probability where they can be found, but electron doesn't occupy the cloud.
Electron is always a point, no matter what wave function it has. Therefore, from this perspective space is all empty.
If you invoke path integrals and infinitely many things bubbling in and out of existence, space suddenly fills up. But the author doesn't even mention that.
If you want to understand this stuff, read up Feynman's descriptions & lectures on QED.
Downvote for this article (sorry).