[This is part of a series of discussions on the craft of modeling conversation. For previous installments, see my original Homer in Silicon article which lays out the basic elements of the model, and previous blog posts on the issue.]
If we have an NPC with a long list of things to say, and the player types WAIT or LISTEN rather than selecting any of the possible responses, we might want the character to comment:
“Next, you’ll need to approach the farmhouse from the northwest under cover of darkness. Wolf-cub should already have cut the telephone wires and the electricity, but you’ll still need to be stealthy: they may be armed.”
You could ask whether the enemy will have snipers.
You continue to attend to The Fang’s briefing.
“Next you’ll… [more stuff]”
The Fang seems to be done.
“You catch all that, Snakemouth? You know I don’t like it when operatives have no questions. It worries me.”
You smile serenely. The Fang mutters something rude under his breath, but it looks like he’s going to let you break for lunch at last.
One simple approach is to keep a counter that resets every time the player speaks, and increments every time the NPC does; thus if the counter hits (say) four, that means the NPC has talked for four turns without any reply, and we can use that information to plan an immediate optional question about why the protagonist is being silent.