Studies have explored how second language (L2) learners engage with peer feedback in instructional contexts. However, how learners engage in self-initiated and self-directed feedback practices beyond the classroom in online spaces is largely unknown. Informed by an ecological perspective, an in-depth exploration of the dynamics and underpinning mechanisms of learners' engagement with written peer feedback on an educational social networking site for L2 writers was conducted. Longitudinal data on 11 language learners' interactions on the platform were collected. An analysis of their interactions on the platform over time and their responses to semi-structured interviews revealed that how they perceived and acted on feedback changed over time. Furthermore, these changes were intertwined with various individual and contextual factors. The findings suggest that encouraging socially related feedback, enhancing certain platform affordances, building a sense of community belonging and helping learners reconceptualise the platform in relation to their language learning are critical elements of enhancing learners' engagement with peer feedback. They also indicate a need for a dynamic and holistic approach to understanding and supporting learner engagement with peer feedback beyond the classroom.