An online forums consist of a board and lots of topics.
What would an offline version look like?
What if we do it in pen and paper. To start a new topic,
you get an empty journal with a wide spine. You write
topic on the spine, then you place the book on a vertical
the top are the most recently written on, and
books on the bottom are the older ones.
You could place such system anywhere on libraries,
Oh, and best of all, it can survive without the internet.