Contemplations from Touhou Tycoon, a Korean Touhou fanpage that has some great articles about the Touhou universe. The following articles are translated from that website for this Touhou wiki.
1. A Barrier Between Canon and Doujin
2. A Barrier Between Game and Scientific Reasoning
3.1 Characters with Secrets Pt. 1
3.2 Characters with Secrets Pt. 2
4. How Can Kaguya and Her Baddies Hide from the Moon?
5. Language Gap in the Red Mansion
6. BGM Shift between PCB and IN
7. What Makes People Play Touhou Series? ]]
8. Too Much for Flying Miko.
9. Witches with Flying Brooms Beware of Hemmorhoid
10. Analyze: "Hajimemashite"