Cleaning Up the Streets: Understanding Motivations, Mental Models, and Concerns of Users Flagging Social Media Posts

Social media platforms offer flagging, a technical feature that empowers users to report inappropriate posts or bad actors, to reduce online harms. While flags are often presented as flimsy icons, their simple interface disguises complex underlying interactions among users, algorithms, and moderators. Through semi-structured interviews with 22 active social media users who had recently flagged, we examine their understanding of flagging procedures, explore the factors that motivate and demotivate them from engaging in flagging, and surface their emotional, cognitive, and privacy concerns. Our findings show that a belief in generalized reciprocity motivates flag submissions, but deficiencies in procedural transparency create gaps in users' mental models of how platforms process flags. We highlight how flags raise questions about the distribution of labor and responsibility between platforms and users for addressing online harm. We recommend innovations in the flagging design space that assist user comprehension and facilitate granular status checks while aligning with their privacy and security expectations.