Although emotional reactivity to social rejection has been examined in patients with borderline personality disorder (BPD) in several studies, the effects of other aspects of social feedback, such as evaluation of one’s opinions that concern self-esteem, have not been addressed yet. The objective of this study was to examine emotional responses of BPD patients after exchanging personal opinions in a new, ecologically valid virtual peer interaction paradigm (“chatroom paradigm”). In this paradigm, 21 BPD patients and 21 healthy controls received peer feedback on their own statements and rated the intensity of their own emotional responses (happiness, sadness, anger, and shame) and the self or other affirmation in response to agreement, disagreement, and neutral statements. Across all social feedback conditions, BPD patients reported more intense negative emotions and less happiness than healthy controls. While healthy controls showed a “positivity bias” for any type of social feedback, the emotional responses of BPD patients’ corresponded to the valence of the feedback; that is, they were happiest after positive than after neutral feedback and least happy after negative feedback. Disagreement resulted in more intense anger and less other affirmation in both groups but only BPD patients also experienced higher shame in this condition. This is the first study to assess emotional responses to social feedback in an ecologically valid chatroom paradigm. Our findings underline that more negative emotional reactions in everyday interactions play a central part in interpersonal difficulties of patients with BPD.