I'm surprised that the poster QUINE hasn't pointed out that mass terms denote a funny kind of substance. Quine the philosopher tried to cash out, e.g., water, as a "single scattered object". You could do the same with space (though this would work far better in a Newtonian universe). But then, almost no one thinks Quine could be right about this (after all, it's absurd to think that water is a single object, but its constituent parts, like 'this water' or 'that water' are not discrete).

Point being that Krauss seems to have presupposed an interesting dualism about the universe: there are things, and where there are no things, there must be 'nothing' -- of the sort people are calling 'metaphysical nothing' (or is it 'physical nothing') here, for some reason. But this description isn't quite accurate, and I'm sure Krauss knows this, intuitively. The distinction between regions of space with ordinary particulate matter in them and regions of space without these isn't the distinction between 'something' and 'nothing', it's the distinction between 'things' and 'non-things'. But non-things are not necessarily nothing. And that's a large part of the conceptual confusion going on here.

Krauss's claim "If “something” is a physical quantity, to be determined by experiment, then so is ‘nothing’." is absurd. The negation of (a) physical quantity is not a physical quantity -- duh. This sort of unreflective empiricism is absurd on the face of it.