While much feedback research in L1 and L2 writing has been conducted in pre-university and university contexts, little attention has been paid to supervisors' comments at the graduate level. Specifically, the nature and role of supervisors' commentary on the writing of graduate-level academic genre is under-explored. Designed to fill such an important void in the existing research literature, the present study, framed by the socio-cultural theory, aims to explore the nature and role of supervisors' written comments on doctoral research proposals. A primarily qualitative analysis of the drafts of three doctoral research proposals, the written comments in the drafts of these proposals, and interview data with three Phd applicants and two prospective PhD supervisors revealed that supervisors' comments on doctoral research proposals were primarily feedback-oriented rather than assessment-focused. Such a commentary practice played an important role in facilitating the initiation of the applicants into the academic community through scaffolding the academic writing process, building a quasi-supervisory relationship, as well as enhancing motivation and confidence. The paper concludes with the implications of the study, as well as suggestions for future research.