Comment threads on web publications, especially when related to contentious stories, can become similarly heated, but the impact of disputes between two parties can be much more wide-ranging. The tone of reader engagement can lift or sully a digital publication enormously: affecting readers' relationships with each other, the value of the published content, editorial ideas, editorial-reader relationships, commercial partnerships and website traffic. Here we explore how and why these factors can be affected, and why paying careful attention to your community engagement – whatever the size – is essential.