How is "word choice" similarity calculated? If you have a high similarity with someone, does that mean your range of words is the same (perhaps because you wri

How is "word choice" similarity calculated? If you have a high similarity with someone, does that mean your range of words is the same (perhaps because you write on the same topics) or that your word frequency is the same (because you have similar patterns of speech)? Are quoted sections filtered out? URLs?