Blocking other users is a common act on Twitter but one which is underexplored from a scholarly perspective, particularly the analysis of mass blocklists. Although traditionally associated with harassment, blocklists are increasingly engaged to create individualised environments that align with users’ personal convictions and exclude apparent transgressors. This study uses a pro-choice blocklist (Repeal Shield) created during the 2018 Irish abortion referendum campaign to explore how users interpret these altered boundaries and blocklists’ influence on the Twitter landscape. A metaphor analysis of more than 2,000 tweets discussing the blocklist highlights the dominant concepts in how users visualise Twitter as both a personal space and a battlefield, in which mental health is a key factor. By drawing on discussions of spatiality, agency, gender and online interactions, we can see how these blocking affordances allow users to exist in spaces in which they construct their own parameters to feel safer, raising questions about how harm, health and risk are understood. The article explores how users make sense of conflicting images like ‘safe spaces’ or ‘echo chambers’, highlighting the apparent policing role held by blocklists. Users are negotiating the type of civic space in which they want to exist as norms of engagement versus avoidance collide; although digital spaces have always accommodated fragmented interests, the technological affordances of blocklists provide more rigid boundaries, highlighting how the evolving architecture of social media allows users to redefine the parameters of their own online spaces.