I do believe that Luna can be direct when she *needs* to be - such as when everyone around her would be unable to understand her allusions or whimsical direction pointings. The case in point that I'm thinking of is her comment in OoTP when they need to get to the Ministry and they can't figure out how to get they and Luna says, "We fly, of course." Some how I don't imagine Harry and crew going "Oh, yeah, right, the Thestrals!" I do think Luna had to go, "Yoohoo, dunderheads..." though in a much more Luna-like fashion. No offense meant to the dunderheads, of course. meh.