I went through a bunch of questions to see if I could categorize them based on your categories. It kind of worked, but I needed to tweak it a little bit for it to seem logical (to myself at least).
I ended up with the following categories. I took questions as I read them and categorized them, making each one a link in the appropriate topic.
Almost every topic I encountered fits fairly easily into one of these 5 topics, although some were a little tricky, either because they could fit multiple, or because they don't seem to fit any too well.
Overall, it doesn't seem too difficult to divide questions into categories, but I don't know if there is a need. In most categories, you already see a lot of common tags. Although it MIGHT help to have the over-arching category that have implied sub-tags to clean things up and standardize them a bit.
- World Creation: planets, astronomy, stars
- Language Development: language, world-building-process
- Plot Development: (this one has a TON of different tags)
- Magic/Technology Development: alternate-history, alternate-worlds, physics
- Creature Design: Evolution, creature-design, biology