Hmmm. I never would have thought of this as a solution. But I don't see diamond "dust" as being any more effective at the "Gee Whiz" factor than other types of metallic or metal flake paint. Diamonds themselves may be high on the hardness scale, but it's the medium in which the "flakes" of any kind are encapsulated that is the "weak link" so to speak. WAY back in the day (1960s) when metal flake paint was real popular among hot rodders and especially kustom car builders, the clear lacquer in which the flakes were carried and applied that was relatively soft (though not as soft as enamel) and it had a terrible propensity to turn yellow if exposed to normal sunlight conditions.
Great advances have been made in transparent top-coat/clear-coat media, although I don't see a disproportionate use of metal flake paint jobs. Most of 'em are limited to dashboards and other interior metal surfaces, although some painters use House of Kolors metal flake with nice looking results. I haven't looked into the current carrier media's resistance to UV exposure-caused yellowing, though.
Finally, I bet one could get the same effect by using cubic zirconia or other prismatic, reflective "chunks" in paint. I see a lotta stuff like that at car shows.
RtR