Emoji are often used to express emotions or visually enrich text communications, but little is known about the impact of emoji in peer feedback. We conducted a qualitative study on emoji's roles in peer feedback in a small group collaborative design activity; the activity was conducted entirely online as part of a distance education class. Using content analysis on the feedback peers provided, and thematic analysis on transcribed interviews, we analyzed how emoji are used and perceived in four types of design feedback. Our analysis suggests that emoji increase peers' awareness of affective status, and are also used to mark minor cognitive feedback with a more personal flavor as part of document-based conversations. We found that emoji help to establish a general informality for peer feedback activities. We discuss the implications for the design of collaborative learning software that supports richer peer feedback.