You’ve done the hardest parts of writing a blog post: Gotten the reader to your site, evoked a strong enough emotion to make them feel they need to add to the discussion and leave a comment, and they submit it and see this:
"Your comment is awaiting moderation”
"Your comment is awaiting approval”
"You need to register first”
Congratulations, you’ve just halted the conversation on your post.
For the most part, moderation is used to stop spam from appearing not necessarily to censor comments, but you’re hurting the voice of the very people that can be your biggest evangelists.