I've disabled comments by unchecking "Allow people to post comments on new articles" In Settings -> Discussions. But comments are still showing in my posts! How do I completely disable comments in all posts?
Are you running any additional plugins that allow comments? If so, you'll want to disable those. I'd also suggest testing the comments yourself by trying to write one and seeing if it displays.
You may also want to ask your question at the official Wordpress forums to see if anyone there has a solution for you: http://wordpress.org.