First of all, you can have any sort of features you want. So you could certainly look at things like sentence structure, pairs of words and so on. More importa

First of all, you can have any sort of features you want. So you could certainly look at things like sentence structure, pairs of words and so on. More importantly, I used "pattern" in a very general sense: there is strictly more structure to a post generated with this system than a random post or even a human-authored one. So repeated words between posts are a pattern, and a very important one at that.