Cannot Comment or Link to Specific Posts

Have you enabled comments on posts in your admin?

Where you create/edit posts or pages in admin, check if you have ticked comments for your posts/pages in the “discussion” box below the editor.

If you don’t see the “discussion” box there, in the ‘screen option’ dropdown field (located near the top right), there are tickboxes to show the ‘discussion’ box for the posts/pages. Tick mark it. In the ‘discussion’ box below the post/page editor, you can then allow/disallow comments for the page.