A socio-constructivist approach to writing pedagogy recognises the importance of participant relationships in argumentation in disciplinary writing, although awareness of the rhetorical resources available to achieve this dialogic partnership between writer and reader can be difficult to teach. The highly metadiscursive nature of feedback commentary, however, offers the potential to scaffold such learning as part of a dialogic feedback cycle. Taking as its starting point, the concept of feedback as genre, this study investigated metadiscourse use in feedback data from the researcher’s own teaching practice. A corpus of 627 formative comments, comprising 16,660 words and providing feedback on argumentation in first-year undergraduate texts, was analysed with reference to Ädel’s (2017, 2018) recent findings and observations, which called for a re-defining of the function and definition of metadiscourse. Findings from the current study include a similarly high frequency of metadiscourse use in feedback to that found in Ädel’s work and corroborate the validity of her suggested multidimensional model of metadiscourse. Additionally, examples from the corpus show the complexity and fluidity of the writer and reader roles. Frequencies of types of metadiscourse markers varied depending on purpose, reflecting either the response of “teacher as reader and dialogue partner” or the pedagogical response of “teacher as knowledge resource”. Responses worked “intratextually” and “intertextually” by extensively referencing both “current text” and earlier stages of the wider feedback discourse chain when identifying and providing rationale and resolution for problems in the development of argument in the text.