Well, I'm stumped. Never heard this phrase in my life.
A "curtain talk" or "curtain speech" is when someone comes out before a play or other entertainment begins and says a few things ("we'd like to thank the members of the board...please turn off your cell phones...the role of Diana will be played tonight by Eve Backstabber" etc). Could that possibly be what the author means? That would work in the context of preceding the "real" conversation, and being inconsequential and unnecessary.