The development of information and communication technologies has resulted in the emergence of new kinds of academic genres and literacies. The more recent social web applications empower learners to create online content in a collaborative way. This paper focuses on the use of wikis in the course of Effective Communication in English. It aims to describe how the course wiki was used to teach writing for academic and professional purposes, and to analyse what impact using the wiki had on the writer-reader relationship. The case study employed several research techniques, including participant observation, text analysis and a self-report questionnaire. The texts published by students on the wiki were examined for reader-oriented features and interactional metadiscourse resources. The results indicate that using the wiki for writing activities made students pay close attention to grammatical correctness and structural coherence. Nearly 60% of the students reported that writing on the wiki made them consider their audience. The extent of the writer-reader interaction was further confirmed by a high use of engagement markers in the argumentative texts. Thus, writing on the wiki can contribute to raising awareness of the audience and to increasing the use of interpersonal metadiscourse. (Contains 2 tables, 1 graph, and 1 figure.)