In the following description we will discuss each kind of discourse object separately.
It is important to note that the evolution of the topic structure (tree) is a very dynamic process whereby much time and energy may be spent on one level of the tree, with members generating many issues and comments before resolving the sub-topics to be later explored.
The explication of the subject space is accomplished by iterative decomposition and community nominations. To anticipate the detailed description, later, of one of the mechanisms of consensus, we mention here the dynamics of how the topic tree comes to represent a "best view" of the subject space.
In essence, though any CM may nominate a sub-topic under any existing topic/sub-topic, in fact, the community as a whole may not agree with that nomination.
We will describe the process of commenting later. But for now, note that when there is little or no support by the community for the nominated topic, then over the course of time that topic will simply disappear. This happens in a straightforward manner. See Memory Effects