Since 2001, the author has researched the value of asynchronous discussion for student learning, with the support of the Visible Knowledge Project. Many of the author's observations about the value of asynchronous discussion were previously documented by other researchers. The author has found that asynchronous discussion can involve more students, more completely and actively, than traditional face-to-face discussions. He has also found that the different structuring of time in asynchronous discussions can alter the way that digression functions, transforming supposedly problematic diversions into engaging and productive learning tools. Rather than working as a distraction or a waste of time, digression in asynchronous discussion can be a productive process, with positive effects for student satisfaction and higher-order learning. The author discusses the positive effects of digression and the challenges of digression as active learning. Some practical considerations are necessary in order to create discussion environments that encourage productive digression. These considerations include (1) decisions about the overall goals of discussion; (2) the design of discussion prompts to encourage those goals; (3) structured rewards for participation that meets those goals; and (4) a "restrained presence" on the part of instructors.