1. "delusion" -- Not actual delusion. Maybe a compulsive reaction to unpleasant reality? When discussions in the staff room turn bad for her, Rikka drifts off into
chuunibyou fantasies that make her feel better but do not actually solve the problem. You could also call it childish -- middle-school age child -- because it does not match reality. In Dekomori's and Nibutani's cases, perhaps they were driven to it by the fact that (a) they were too smart to find school work challenging, and (b) their intelligence and pride made them objects of dislike for the other students. Dekomori had to go to a higher grade to find a friend; Rikka had to go to a lower one. The reason Rikka had no friends may show up soon in the anime. I guess her parents' divorce will be part of it.
2. Early this morning (actually Thursday evening Tokyo time) there was a live broadcast of an open recording of the show's radio program, featuring the four main female seiyuus. They all showed up in full gothic lolita outfits. I have put
a post with pics in the Voice Actor thread.