Typical LMSs---specifically threaded discussion forums packaged within them---often fall short in supporting collaborative discourse. Prior research has documented a myriad of pitfalls of discussion forums. For instance, \citet{Hewitt2005-vr} documents premature abandonment of discussion topics partly because of learners' "single-pass discourse practices;" that is, as participants of threaded discussions tend to make single passes of unread posts, threads without recent notes are likely to die, leaving potentially promising ideas untapped. \citet{Thomas2002-nh} argues the threading structure of discussion forums leads to branching and increasingly fragmented conversations, with repetition and duplication appearing in different threads; as a result, many discussion themes remains underdeveloped, with little idea exchanges taking place in their corresponding threads. The rigid design of traditional threaded discussion environments restrains ideas within threads, and consequently suppresses the flexible movement of ideas across discursive contexts, the creation of higher-order organization of ideas, and the self-organization of discourse participants around ideas \cite{Scardamalia2003-hp,Scardamalia2011-lo}.