I was wondering what would be the reasons for making a person sign up to your site, this would only block SE from certain content that logged in users can see and also limit and annoy my traffic? So why include it?
Reduce spam comments? Build an email list? WP registeration doesn't have to exclude content, the default is 'register to comment'.
Just to avoid spamming the comments section for your blog, ideally we should not enable comments on a new blog. You should open the comments section only when you have right anti spam installed. However you have not mentioned what type of blog you have (free hosted or own hosted).