By toggling the visibility of WordPress comment form it comes visible only when a user clicks the comment button on single post pages. You can easily show/hide comment form via AJAX by using Show/Hide Commentform plugin, the plugin works with all WordPress and BuddyPress powered themes and there are no configuration options to set.
Simply install and activate Show/Hide Commentform plugin and you are done. It starts worksing as soon you activate it. Open any single post page and click the small Comment icon, it instantly drops down a comment form.