Journalistic professionalism serves as a semantic tool for journalists to draw boundaries and to demarcate their profession. This research builds on Andrew Abbott’s book The System of Professions: An Essay on the Division of Expert Labor, and his assessment of journalism as a ‘permeable occupation’. By way of a strategic case study of a German-language news organization, it puts forth the notion of journalism as a profession of conditional permeability in certain participatory online settings. This research traces how journalists at a case organization used professionalism to delineate their own job from two groups of interlopers in online news spaces: Community managers tasked to moderate user comments, as well as audience members who participate by way of commenting on the news. The study draws on a case study of a market leader and early adopter in community management and comment moderation – with evident limitations as far as generalization to other contexts. Journalists used concepts deeply entrenched with journalistic professionalism, such as writing skills, gatekeeping and the application of news judgment to invoke boundaries between professionals and nonprofessionals, but also acknowledged unboundedness within particular subdomains of their work. While journalists asserted control over a journalistic epistemology, practice was partly open for other professionals, such as community managers, but closed for nonprofessionals. Some identified a hierarchy of professions, with community management serving an assistant function to journalism. The concept of conditional permeability accommodates both blurred boundaries towards other professional actors and distinct boundaries towards nonprofessional actors.