I joined the HN community because I was interested in the Ycombinator program- I imagine that most people joined for a similar reason originally.
I've remained a member of the community primarily because I enjoy the discussion. While I can find the links anywhere, I really enjoy discussing and debating issues in an intelligent and civilized manner, while learning what's interesting to my peers.
Maybe not requiring local launchly accounts (by using Disqus for comments) is actually going to work against me on the community building side of things?