The mastery of academic writing is essential in doctoral writing. Supervisory feedback provides opportunities for students to improve their writing. It is a communicative tool that can be categorized based on fundamental functions of speech: referential, directive, and expressive. This study provides some understanding of the impact that language and speech functions have on the learning experiences of doctoral students. Sources of data are oral interviews with each student, and their supervisor’s written feedback on drafts of that student’s thesis. Analysis of the feedback provided useful insights into the type of feedback the student considered useful for their development. The students found value in all three types of feedback. In particular, expressive types of feedback often led to an emotional reaction, as students viewed praise, criticism and opinions as motivating or challenging. We argue that expressive types of feedback can play an important role for developing academic writing. This study assists supervisors to acquire a higher level of language awareness so they are better equipped to provide feedback that supports the academic writing and overall learning of their students.