You

You - the second-person singular. YOU always binds to the addressee of the command: either the player character, or the actor being given orders via a construct like ACTOR, DO THIS.

Binding to the PC is grammatically correct in a first-person narration, because the PC is the narrator's ME and therefore the player's YOU. It's less so in a second-person game: the PC is the narrator's YOU, so the player's YOU ought to be the narrator. However, some players are literal-minded about second-person narration, so rather than reflecting the narrator's YOU into the player's ME, they simply say YOU too. Fortunately, there's not any serious ambiguity here. The narrator is typically not a game-world object, but is an entity that exists outside the game world, so it's off-limits for discussion in commands. So YOU can't mean the narrator. That means that if the player uses YOU at all, they must mean the PC.

You : Pronoun

The second-person pronoun binds to information contained within the command itself, namely the addressee of the command, so we need to resolve it using the parser's "late binding" scheme. That is, we return 'self' to tell the parser that it needs to go back and resolve this pronoun after resolving other phrases.