Peer review is applied as a powerful tool to enhance student collaboration online writing. The purpose of this paper is to analyse learners' mechanisms of peer reviewing in the nature of student interventions and interactions in written online peer reviewing and how categorization of student comments can be used as a means for analysing student peer reviewing. The study is an in-depth investigation of computer science students participating in a technical writing course, using Google Drive as their joint work space. While writing their group text, the students were participating in peer reviewing work. Results show combining analysis models provide a better understanding of the implication of commenting in both scrutinizing the progressive scale of assistance, as well as area, nature, and type of commenting, together with what themes evolve. Further, taking turns providing feedback is an enriching activity.