Problem: Many of the close reasons are self-explanatory, but a few would benefit from having the descriptive text shown when viewing closed questions. (For example, my recent comment on "Not A Real Question".)
Proposed solution: Simply sticking it in a normal size font in a paragraph below "closed as ..." seems the appropriate place.
NARQ would probably benefit disproportionately more from this than the other reasons. (Or have I misunderstood NARQ?) However, it seems like it would be helpful to new users that get their questions closed and would otherwise have to search meta or discover the title text for the close reason. (Though many 3k rep users seem to not realize these descriptions exist either. I didn't notice the text till around 6k rep, I think.)
And yes, the text is already retrieved and sent along with the page, but it's completely non-obvious you can find it the title text IMHO.