Textual consumption in digital spaces has come under scrutiny by educators who worry about youth's surface-level comprehension of such texts as well as the polarizing nature of online discourse. This paper synthesizes affective concepts of critical witness and glimmers of care to explore two cases in which adolescent writers in digital OST programs engage with digital communities surrounding texts like comics, movies, and video games. We trace how focal youth across the programs engage in critical witness around issues of marginalization in digital spaces outside of class in order to produce advocacy-focused compositions addressing issues they encountered and discussed across informal digital learning spaces. We identified a common trajectory across both cases for these youth advocates: (1) experiencing and witnessing marginalization in digital spaces outside of class; (2) bringing critical witness to (digital) class; leading to (3) constellations of advocacy produced through compositions. Teachers can support such adolescents through affectively attuned instructional practices like framing spaces to center youth voices, providing multiple channels for peer conversation, inviting youth to co-design expansive and creative assessments, and cultivating reciprocal understanding of power and vulnerability through practices of critical witness.