An online system receives a posted content item from a posting user. The online system labels the posted content item with an audience, the audience being a subset of a group of users having an affinity to a topic of the online system, the subset of the group of users sharing a particular treatment regarding the topic. After identifying an opportunity to present content to a viewing user, the online system selects candidate content items, and scores each candidate content item by determining whether the candidate content item is associated with an audience that includes the viewing user, and if so, modifying the score of the candidate content item to be higher. The online system ranks the candidate content items based on the associated score, selects a subset of the candidate content items based on the associated ranking, and presents the selected subset to the viewing user.