In this paper, we highlight a concern with using online discussion for learning. We argue that there is a lack of technological support for the development of personalised knowledge representation for most online discussion forums. Analyses of existing discussion forums suggest that there is a range of collective knowledge representation mechanisms which support a group or a community of learners. However, such mechanisms may not necessarily lead to learners’ internalisation of collective knowledge into personalised knowledge. We discuss how internalisation can be facilitated through the notion of knowledge objects, while externalisation can be mediated by idea artefacts. These notions are translated into technological supports and suggestions of how online discussions can be designed differently from the common threaded discussion.