Yes, it's coincidental rather than unsupervised... The fact that to have a good "next character" prediction, you need to know about the "mindset" of the author makes sense. Especially in the context of product reviews.

Had they created a next-move predictor for chess, they wouldn't have been surprised to find a neuron representing the aggressiveness of the player.

It's a good result on its own but the word "unsupervised" is a bit annoying.