Drupal by default has functionality that allows users, both authenticated and anonymous depending on permissions, to post comments to your site, if you allow it.
When you are creating or altering a content type, you can set the commenting for that content type.  After setting up your content type or altering an existing content type scroll down to the Comment setting tab.  Note, this is for when you are creating/altering a content type and not creating content.

On the Comment setting tab you will see several options.  The first option, Default comment setting for new content, determines the basics of your commenting

  • Hidden - Comments are not allowed.  If comments were created in the past, these comments will be hidden and not display to the user.  If you select Hidden, none of other options apply.
  • Closed - No comments.  If you created comments in the past, these will be viewable.
  • Open - Comments!  Comments will be allowed to be entered and comments will be shown.

The next option is threading.  Threading nests and indents the comments in a hierarchical fashion.  This allows the user to see the flow of comments.

Comments per page is allows you to determine how many comments will be displayed per page.  The choices range from 10 to 300.

Allow comment title allows the commentee to enter in a title to his comment.  This field is not required.  

Show reply form is on the same page as comments is confusing and messy.  If you check this box, the user will have to click a link to get to the comment entry box.   

Preview Comment has three options.  

  • Disabled  will not show a preview of the comment before the user adds it.  
  • Optional allows the user to see their comment, if they want, before the save it.  
  • Required, forces the user to see it before it is saved.  If you do not give your users the permission to edit a comment they previously entered, it is recommended that you force the user to see, thus review, their comment before they commit it.
In this example, preview is optional, comments are 50 per page, comments can show title, the reply form in visible, and threading is active .  All these settings mean nothing since hidden is selected for the setting.