In this paper, we built an agent -based model to integrate and synthesize social science theories to inform online community design. As an ex ampl e, we use the model to examine how various styles of mod erating online conversation s affect community performance . We compared three styles of moderation – no moderation , in which all members are exposed to all message s; community -level moderation , in which off -topic messages are deleted for the group; and pers onalized moderation , in which different messages are shown to different individuals to match their interest s. We examined the effects of these moderation techniques in communities with various topical breadth s and message volume s. Virtual experimental resu lts suggest that despite the widespread use of community -level moderation , personalized moderation was more effective in in creasing member commitment and contributio n, especially in communities with a broad set of member interests and high message volume. Compared with no moderation , community -level moderation increased members ’ likelihood of reading but not posting messages .