Have you ever wanted to change text formats for your site's comments?

In my case, I wanted all comments done only in plain text no matter if it is a signed in user (authenticated) or just an anonymous one. Formats for contents still depend on the original settings - this only affects text formats for comments only.

So how to force a plain text comment? Here's how to do it:

1. Firstly, enable Field and Field UI modules
2. In your Drupal dashboard, goto "Content Types", select "comment fields" tab
   
3. Click "Edit" for Comment label
   
4. Change to Text Format to "Plain Text"
5. "Save"

That's all there is to it!

Now whenever a user needs to drop a comment for your blog post, he/she can only do it in plain text only..

Do the same for your other content types such as book type etc as you desire..