A Writer would be someone who does creative story writing involving action intent for players , character speech lines for NPCs, and world lore.
The basic idea behind it would be that the Writers design the quest storylines based around what the Builders have built in the world. They would be writing story lines explaining the necessary interactions and actions of the player to complete the quest or adventure.
The Coders would then take the story lines from the Writers and program them into the adventure world.