I wonder if the dimensionality 14 is something intrinsic to idea spaces in general, or if they're actually measuring the dimensionality of the human brain's storage of ideas? Or something about the English language even?
For me, any such number is an artefact of the data -- they've included things like the name and demographics of the idea's author, which will be clearly useful in practice for a "Show me more ideas like this" application, but which will only be misleading if trying to study the nature of "idea space".