Existing studies have measured the effect of video-based feedback on student performance or satisfaction. Other issues are underacknowledged or merit further investigation. These include sociocultural aspects which may shape the design and implementation of video-based feedback, the ways students use technology to engage in feedback, and the processes through technology may transform learning. This study investigates the design and implementation of a video-annotated peer feedback activity to develop students' presentation skills and knowledge of climate science. It explores how their use of a video annotation tool re-mediated established feedback practices and how the systematic analysis of contradictions in emerging practices informed the subsequent redesign and reimplementation of the approach. Employing a formative intervention design, the researchers intervened in the activity system of a first-year undergraduate education module to facilitate two cycles of expansive learning with an instructor and two groups of Hong Kong Chinese students (n = 97, n = 94) across two semesters. Instructor interviews, student surveys, and video annotation and system data were analysed using Activity Theory-derived criteria to highlight contradictions in each system and suggest how these could be overcome. The findings highlight the critical importance of active instructor facilitation; building student motivation by embedding social-affective support and positioning peer feedback as an integrated, formative process; and supporting students' use of appropriate cognitive scaffolding to encourage their interactive, efficient use of the annotation tool. Conclusions: In a field dominated by experimental and quasi-experimental studies, this study reveals how an Activity Theory-derived research design and framework can be used to systemically analyse cycles of design and implementation of video-annotated peer feedback. It also suggests how the new activity system might be consolidated and generalised.