Are questions about videogame creepypastas and video game theories in scope of the site? Given by the way I understand description of the site I think they should be included and accepted. But should they?
You're fine to ask if a creepypasta is actually a creepypasta and not just something somebody made up on the spot. For example, our questions about Herobrine (1, 2) are well received. Everything else becomes automatically speculation about the game, and therefore off-topic for us.
If by game theory you mean these sort of theories, I am afraid they would be in general off-topic: they present a number of facts about a game and offer their interpretation thereof. What's there to ask? If you wanted to know if one of the facts presented was real, Arqade would probably be able to help. If you're looking for confirmation that a game theory is (or isn't) true, that falls under "developer intent" and "game design" (as in, "what did the author wanted these things to signify? does the game design support this idea?"), with the usual rare exception of the explanation being offered in-canon.
I think this is a rather bad topic for our main site.
Arqades main focus lies on strategy, gameplay and in-game problems. We also accept some Lore and Technical questions but these should be answerable by someone who plays the game or is familiar with the game.
The problem with Game-Theories is that they are well... Theories. Often there is no evidence to back up an answer. Most questions would fall under the close category of "Developer intent" or too broad.
Then the thing with creepypastas: A creepypasta isn't even always related to a game. It's a small horror story on the internet. While some of the more popular ones are related to gaming or games, a lot of them are not and we couldn't allow all of them.
Let's take Ben Drowned for example. It's one of the more commonly known creepypastas about a "cursed" Legend of Zelda - Majoras Mask game. But even for this specific case you're better off asking questions on a different site. Skeptics and Gamedev come to my mind here.
Two example questions about this creepypasta:
- Is the "cursed" Ben Drowned game real? - Skeptics
- How was it possible to achieve the effects of the Ben Drowned video? - Gamedev/Video
Now while I would tend to close questions about these two topics on the main page, you can still chat about them with other people in The Bridge or maybe you could even create or ask for a new chatroom that focuses on this very topic. I actually kind of like game-theories/creepypastas and I'm pretty sure that a lot of other people on this site are interested in them aswell but it's not a good topic for the main site.