Horst is really shrewd and well-spoken for a Discworld troll. It's hard to make out in the dark scene, but there's something moving up and down above his head when you speak to him in his residence: a fan that's keeping his brain cooler, much like Detritus's cooling helmet. Troll brains work better at colder temperatures.
Subverted: When you first meet him Lewton's narration points all this out. And later in the game, he's out and about without a punkah-wallah in attendance and shows no sign of getting dumbed down.
Lewton dresses in a trench coat, fedora, and has his name on the door because the Discworld runs on the power of Theory of Narrative Causality. As the Disc's only private detective, he's required to follow all of the tropes to a tee.
A subtle one. The last time Nylonathotep was invoked, thousands of years ago, the sacrifices forming the octagram were situated at various points around the Circle Sea. During the time the game takes place, the octagram only covers Ankh-Morpork, and Nylonathotep is still huge enough to be a formidable threat. Just how big was it the first time around? It is possible that there are no records of its reign of terror because no civilizations survived.
Who says all of the Circle Sea was sea back in the past? Might have the land sank or was destroyed when Nylonathotep was banished the first time around, thus forming the sea and destroying the civilization that has summoned it.
