How do you stub out a community? If the community is engaging, people will be more likely to comment (like HN), but if you are a site, you really don't have tw

How do you stub out a community? If the community is engaging, people will be more likely to comment (like HN), but if you are a site, you really don't have two separate communities to swap in/out in the user's mind. Additionally, even if you did optimize your site design/functionality to increase comments, is that really desirable without an engaging community in the first place? Would everything end up being nothing that adds to the conversation? (see Youtube)