Membership

Unless you have a specific reason that you want people to be able to register,, it is better to leave this option unchecked. I would delete all the users that have registered as well.

Once people (or bots) are registered they are able leave comments on your site. You already have spam comments on the blog pages of your site — possibly due to this. If you allow comments to be posted you really need to moderate them as it reduces credibility and will affect your search ratings if your site allows spam comments to be posted.

If you are allowing comments, you will probably need a plugin in place to restrict spam such as akismet.

There are other settings which can help restrict comments at settings => discussion see http://codex.ww.wp.xz.cn/Settings_Discussion_Screen