While a great deal is known about instructor response to student writing--from commenting practices to student perceptions--less is known about how feedback impacts students' writing and writerly development. While we set out to study students' explicit engagement with written instructor feedback, our initial experimental design was disrupted by the COVID-19 pandemic. Accordingly, we describe the dialogic collaborative process that emerged as we considered anew both the data we were able to collect and, in turn, feedback. This article proposes that feedback on student writing is a boundary object that affords those interacting with it the opportunity for collaboration despite the different languages, meanings, and priorities they bring to it. The results present an initial framework for theorizing feedback as boundary object, which includes (a) a linguistic comparison of the words used by instructors and students to talk about writing and (b) structural trends that we have termed "dialogic infrastructures," describing the form and orientation of instructor feedback and corresponding student responses. We also share implications of this nascent theory for future feedback research and writing-classroom practices.