Yah, if you're gonna highlight that quote, then as a physicist I can pretty much squash it.

The Planck length is just a number. It's achieved by taking some other constants and multiplying /dividing them via dimensional analysis to come up with a number whose units are length only.

It does not represent anything physical, and any notion of what it might represent is purely hypothetical. As was mentioned, there is no physical way to measure anything that small.

On the point that space is granular on some scale. I take it you mean that on some scale a thing can be at point A or point B, but nowhere in between.

IF this were true, then there would be diffraction planes in space (albeit immeasurably close together, and not necessarily stationary). These planes would alter the way waves travel through space and would have very measurable effects. For one, certain frequencies of light would not travel in certain directions.

Also, quantum mechanics shows that a particle is not a pinpoint-localized phenomenon, but a kind of fuzzy bordered area of probability density. There is no way for a particle to be in a "single place".

Recall the link between position and momentum. The more defined the momentum is, the less defined the position is. Since there are always reasonable limits to place on the momentum, there is implicit uncertainty in the position.

If that's what you meant by granular space, it's pretty well disproved.