I think "postmodernism," "colonial alienation," and "post-utopianism" are all meant to be blanks, which we're supposed to fill in with whatever meaningless term seems appropriate.

But I share your uneasiness about using these terms. First, I don't know enough about postmodernism to judge whether it's a field filled with empty phrases. (Yudkowsky seems to take the Sokal affair as a case-closed demonstration of the vacuousness of postmodernism. However, it is less impressive than it may seem at first. The way the scandal is presented by some"science-types"--as an "emperor's new clothes" story, with pretentious, obfuscationist academics in the role of the court sycophants--does not hold up well after reading the Wikipedia article. The editors of Social Text failed to adhere to appropriate standards of rigor, but it's not like they took one look at Sokal's manuscript and were floored by its pseudo-brilliance.)

Second, I suspect there aren't any clear-cut examples of meaningless claims out there that actually have any currency.(I only suspect this; I'm not certain. Some things seem meaningless to me; however, that could be just because I'm an outsider.)

Counterexamples?

If people agree on what the term means, and they can read a book and detect (or not) colonial alienation, and thus have a test for post-utopianism, and different people will reach the same conclusions about any given book

By hypothesis, none of those things are true. If those things happen to be true for "post-utopianism" in the real world, substitute a different word that people use inconsistently and doesn't refer to anything useful.