Before revision:  We set up a series of predictive exercises , in which users are described using several posting activity features capturing their overall activity levels, their posting success, the reactions their posts attract from users of different stances, and the types of discussions in which they engage.
After revision:  We set up a series of predictive exercises based on machine learning models. Users are described using several posting activity features capturing their overall activity levels, their posting success, the reactions their posts attract from users of different stances, and the types of discussions in which they engage.