What I'm learning from this discussion is that the Touhou fandom is pretty much half MLP fandom and half Homestuck fandom, 'cause it's both girls and guys on tumblr. On the MLP side there are a shitload of female characters that are easily distinguished by an outside characteristic, and tons of remixes of the music. But on the Homestuck hand, lots of people who are part of the fandom haven't actually experienced the source material, just like with some Homestuck fandom people, and the source material is in a shitload of mediums, just like Homestuck.
Also, just like both fandoms, people just fucking love drawing/writing porn of underage characters (or underage-looking, no difference).