There are two things wrong with this. First, you are assuming that a nonzero fraction of people will sign up for every open-membership community available to them, frequent, and vote in each such community. Realistically most people probably can't do this for more than ten communities. Second, even if there is eventually convergence it may not occur quickly. For example, the universe will eventually reach a state of maximum entropy but it isn't something that any of us need to worry about today.
