Source: symbv from evageeks forum.
There is the last page of the interviews with their hand-written messages:
Shinbo's message is at the right hand side.
The one written in red ink is Ume's.
The one below Ume is by Urobuchi.
From the article it is stated clearly that "Walpurgis Night" is a powerful witch, so it is not an event it seems.
Also part of the interview:
- Ume - The discussion among fans have been intense. Unlike an anime adapatation, everyone can join the discussion and do research just like anybody else. This is the key thing with anime with original story.
- Shinbo - The reaction is something that's not happened before, right, Urobuchi-san?
- Urobuchi - This is the first time I experienced such feedbacks. Never before was my name remembered even by overseas fans! It really surprised me.