That section can be styled with CSS added to your style.css. How would you want it to look?
For example, you can change the background color and shape with these lines:
background: none repeat scroll 0 0 #223344;
border-radius: 20px 20px 20px 20px;
You can eliminate the section on a given post by editing the post and unchecking the 'Allow comments' box in the 'Discussion' section below the editing area.
If you can't see the 'Discussion' section, click 'Screen Options' near the top of the screen and make sure the 'Discussion' box is checked.