Mental illness among trangender people is a well-documented problem. Being addressed with the right name and pronoun is an important part in the health-promotion process. In this study, participatory design with transgender and/or nonbinary people was performed, in order to explore how social online platforms can be designed to address the problem of people being misgendered. In interviews, participants described their experiences, which then formed the foundation for a workshop during which potential design solutions were explored. The study resulted in three guidelines that can be used in the design of social online platforms: Selective pronoun visibility, Informative design elements and Community-based functions.