World Modeling is getting curious about how the world works. It’s diving into wikipedia, it’s running a survey to get data from your friends, it’s dropping balls from different heights and measuring how long they take to fall. Empiricism, scholarship, googling, introspection, data-gathering, science. Applying your epistemology and curiosity, finding out how the damn thing works, and writing it down for the rest of us.
The eleventh virtue is scholarship. Study many sciences and absorb their power as your own. Each field that you consume makes you larger. If you swallow enough sciences the gaps between them will diminish and your knowledge will become a unified whole. If you are gluttonous you will become vaster than mountains.
Properly considered, the overwhelming majority of content LessWrong is about modeling how the world is, including almost all posts on Rationality and all practical advice. The intended usage of World Modeling is to capture all content describing how the world is that is not captured by the more specific major tags of Rationality, World Optimization, and AI.
If content warrants a no to all of the above questions, then it is likely to be both relatively pure world modeling (not about optimizing in any direct way) and not already covered by an existing major category. It is then a good fit for the World Modeling category. Stuff like math, science, history
A study of how people historically exercised is World Modeling. Advice on the optimal way to exercise in the present day is World Optimization. A study of the Fall of Rome would be World Modeling. A review of current policies being discussed by people who want to cause changes in a present government should be classified as Optimization. It would be World Modeling too only if it is expected to be of interest to people with no immediate plans to try to alter government, for example a review on the effects of marijuana on productivity, driving, IQ, etc.