Although peer review is widely adopted in tertiary L2 writing classes, students' use of different languages -- or translanguaging -- in written peer feedback remains underresearched. Three studies that have explored the issue -- Yu and Lee (2014), Yu (2016), and Yeh (2018) -- were all conducted on Chinese-speaking participants, suggesting the need for studies in different contexts for a broader generalisability of the findings. To bridge the research gap, this study examined feedback comments produced by 24 Japanese college students. In addition to comparing feedback profiles according to language use, stimulated recall interviews were conducted to determine the factors underlying Japanese L2 learners' translanguaging practices. The findings suggest that most Japanese L2 learners make language choices based on context as a result of the interaction between inter- and intrapersonal factors such as the (relative) L2 proficiency of the peer reviewer and the affective need to mitigate negative feedback. This study adds to the rather sparse literature on L2 learners' language choices in written peer feedback and factors contributing to such decisions.