I'm not a big fan of using this very strict definition for the level design subforum. The way it is now, it just means that Lemmings Discussion becomes a dump for everything that doesn't fit anywhere else. And stuff related to level design, even if it's not theory, fits better in Level Design than Lemmings Discussion (such as Dullstar's topic).
So rather than thinking of Level Design as "Level Design Theory" and Lemmings Discussion as "Dump for everything that doesn't fit anywhere else", I think it makes much more sense to go along the lines that Level Design is "Anything related to level design that doesn't fit in Level Packs (or Lix)" and Lemmings Discussion is "Anything related to the official games". If something doesn't clearly fit into a specific board, it shouldn't go into a "Dump for everything that doesn't fit" board but rather into the board where it's closest to.
Also, I hope "Level Packs" is also not so strict to include only level packs, maybe some people would have a thread releasing individual levels. Such threads should go in "Level Packs".