Anonymity creates a low barrier to entry, facilitating free participation. But at the expense of requiring manual moderation. I don't know how much time has been spent on troll moderation on HN. But let's say you have 100 small sites - moderation could be quite time consuming. And if the sites are too small to allow you to identify trusted users to offload the moderation to (perhaps through some application features), it is doubly problematic. However, identity verification is an easy solution, although at the expense of reducing participation by creating a higher barrier to entry.