How to turn on/off comments on individual posts / pages in WordPress
Ordinarily it exists a general setting for the comments on your WordPress site. They are or OFF or ON. You can subscribe these settings for invidiual posts and pages.
How to turn on/off comments on individual posts
Go to WordPress control panel >> Posts >> All posts >> Edit the post you want to configure >> Click on the “Screen Options” button on the top right side of the page (1) which shows a configuration window >> Check the “Discussion” checkbox (2)
How to turn on/off comments on individual pages
The only difference here is that, obviously, you click on Posts on wordpress editor >> Edit Pages instead of Posts. The next steps are the same as at the Posts.