The characterization of the thesis as a written product has been the contribution of several studies. However, progress is needed in understanding how this academic genre has been gradually generated. In this regard, it is known that the elaboration of a thesis involves an academic expert who guides and directs a novice writer or a group of them through various forms of feedback. This article focuses on the written comments in order to understand their roles in the process of elaboration of a thesis, from the perspective of those participants. With this objective, a phenomenological research was implemented based on in-depth interviews to 5 thesis supervisors and 6 thesis students in the process of obtaining their academic degrees of Bachelor in Education in Teaching Programs in two universities in Concepción (Chile). The analysis shows that supervisors' comments are part of a feedback circle oriented to adjusting students' writing to the thesis genre, which is valued by all participants.