A central question among instructors teaching writing-intensive courses is how to best respond to student writing. This study posits that the margin of the essay should not be reserved for instructor feedback only, and that allowing students to comment on their writing choices in this space has pedagogical aims. This study examined the use of “comment bubbles” to engage students in thinking about their writing choices in argumentative writing in an undergraduate social and economic justice course. Comment bubbles are comments and questions students inserted in the margin of their essays using the comment function in Microsoft Word. The margin of student essays was framed as a safe writing environment to encourage student self-expression beyond that already expressed in the essay. A thematic analysis of student comment bubbles found that students used the comment bubbles to react to research they read in journal articles, elaborate on their writing choices, share their personal experiences, and reflect on their future career interests. Allowing students to comment on their writing choices in this space facilitates student self-expression, self-reflection, and critical thinking.