Enabling a comment form is probably a good idea as it makes it easy for your site's visitors to comment.Previously if visitors had to comment they had to click on a link which would open a pop-up window.After enabling,it's just 2 or 3 boxes!
To enable a comment form, go to the settings section of your blog

See the image and change the settings of the comment form placement
Save changes
After this modification you can see the comment forms below each post.
NOTE: You can also enable smileys for your comments.