While recent research has brought increasing awareness that language use plays an important role in online communities, little has been done to study the association between characteristics of interactions and social relationship in terms of discourse functions. This research study attempts to shed light on the issues in the context of a blog-based teachingportfolio, which serves as an interactive channel for pre-service and in-service teachers in Hong Kong to engage themselves in dialogic and collaborative discussions. Content analysis of comments on the blog and semi-structured interviews were conducted to examine the use of discourse functions and discussion topics. Insights into online learning and recommendations for future research are made.