1. A computer-implemented method of discussion thread management performed by a computer system having at least one processor, comprising: enabling users to define user-defined tags and to associate said user defined tags with posts in a discussion thread; automatically generating system-generated tags, wherein said system-generated tags are determined by analyzing the contents of all posts in a sub-thread of said discussion thread, wherein said sub-thread is made up of a selected post in said discussion thread that is a root post of said sub-thread, posts that are replies to said root post of said sub-thread, and all posts contained in any other sub-threads having root posts located under said root post of said sub-thread; associating said system-generated tags with said selected post; enabling a moderator user to promote a number of said system-generated tags to moderator-promoted tags; and determining, responsive to said user-defined tags, said system-generated tags, and said moderator-promoted tags, whether said sub-thread is off-topic with respect to said discussion thread.