They both symbolize so much of a mess to each other, of their broken pasts and somewhat hopeless futures, that it's only in this between-place they can even have a moment to think about who and what they are. There's a theme running through this episode about Chuck becoming a man, and a theme running through the season about Blair becoming a woman. All the ways they try to define those things for themselves and the meaningless ways they've tried to define them: None of that matters, here in this between-place.
Then they do it.
MEANWHILE IN DUMBO
Vanessa finds a manuscript that apparently Dan's been working on since before the show started, a particularly sad little roman à clef in the Lonelyboy tradition, about how much Dan felt like an outsider for all this time and, just like Gossip Girl suggested at Graduation, has become the Ultimate Insider. If slightly unbelievable, it's not so much as a retcon but more in terms of its radical honesty. Apparently if you go back as far as Milo even, you can see this manuscript lying around à la the Glass Vivier stuff with the constant Blair shoes that I totally didn't pick up on. The book is called Inside, and the only thing more gorgeous than its existence is the fact that Vanessa has found it, is now speed-reading it with her homeschool powers, and will doubtless use it to fuck everything up for everybody, because of how she is.
Sophie, looking amazing: "Louis, I don't know if you've noticed, but Blair's kind of a flake."
Louis: "Don't be silly. I'll wait all night if I have to. Knowing these maniacs, she probably just got abducted by a real estate developer and nearly set on fire, then snuck into a Bar Mitzvah. She'll be here eventually. It's cool."
Lily: "Hey, Carol. No big deal, but Charlie's off her meds and we're scouring the city for her. Maybe you were right."
Carol: "As per usual, this is actually a ludicrously complex scheme to get money out of CeCe, so you just do whatever you want."
Serena: "Charlie! Get down from that window!"
Charlie: "No! I heard you tell Dan and Vanessa that I am crazy!"
Serena: "Look at yourself, look at your choices! Do you want me to go get Dan? His particularly brand of condescending self-righteousness talks the rest of us down off ledges regularly."
Charlie: "I'll never have Dan! That's why I stole your dress!"
Serena: "I don't understand what you mean."
Charlie: "I am sort of winging it!"