By default, comments are automatically allowed with new WordPress websites. When we first create the website, we turn this featue off because you don’t want to automatically allow comments on all the new pages on your website. Often we leave this feature disabled until you are ready to maintain and manage comments on your new blog posts. This is a feature can easily be turned on and off. Simply login into your wordpress backend and go to Settings >> Discussion. Look for the 3rd checkbox and check that in order to enable comments. The comment feature will applies to all NEW blog posts and pages. Now that you have activated this option, with each NEW post you create people will automatically be able to comment. You will receive an email so that you can approve the comment before it goes live. If you would rather just allow people to comment without your approval you can make it so. Go to Settings >> Discussion. Uncheck the 11th checkbox.
This will not affect any existing posts or pages. If you want people to be able to comment on previous posts you must go to those posts individually. Go to Posts >> click on the post you want to allow comments. Scroll down to the bottom of the page to see if the “Comments” + “Discussion” sections are there. If not, scroll back up to the top and click the “Screen Options” at the top right. (see two screenshots below) Check the two boxes… comments and discussion. Then click the screen options to shrink that back down. Now at the bottom of the screen, there are two new sections. In order to allow for comments, just check the box for comments in the discussion section. Then update the page by clicking the blue “Update” button.
Voila… Just note, that if you create new pages… they will automatically allow for comments. So when you create the new page make sure you uncheck this box to disallow the comments on the pages. You don’t want people commenting on you pages, just your blog posts.