Hah, well...I'm friends with Seanan, who is a bestselling urban fantasy author, and a Homestuck fan, and I also like Hannibal. I think they all have a bit to do with it...but it does seem to me that Homestuck and Avengers fandom have the biggest crossover with Night Vale fandom, largely because of the number of fics that have been written where Phil Coulson (of SHIELD) grew up in Night Vale.
You have definitely not been on the same parts of tumblr where my friends and I hang out! "Feels" are not particularly sexual. Unless you count wanting to make someone a sandwich or pinch their cheeks or be *~*~*~*so happy*~*~*~* for them as a form of sex. My friends and I talk about having feels when we see or read or watch or listen to things that make our hearts fill up with emotion, but the emotion is usually some sort of empathy or sadness or sympathy or wistfulness or identification with the character/person who's going through something tough or being cute with someone they care about. I don't have "feels" about people I want to date or sleep with.