In many themes, the comment box isn’t set to show on Pages, but it’s scripted into page.php to display if you set a custom field in the page with a key of “comments”.
Although you don’t need to mess with the code, I’ll show it here in case you’re wondering:
<?php if ( get_post_custom_values('comments') ) comments_template() // Add a key value of "comments" to enable comments on this page ?>
Open the page you want comments on in your WP Admin, scroll down to the Custom Fields area and expand it. Now in the “Key” box type the word “comments” and in the “Value” box type “comments” as well and then click the “Add Custom Field” button. Now save the page and test it in your browser.