I'm not necessarily trying to prevent hot-links. Rather, I am trying to understand what this feature on the Permalinks Settings page actually does:
 Redirect attachment URL's to parent post URL.
Attachments to posts are stored in the database as posts, this means they're accessible under their own URL's if you do not redirect them, enabling this will redirect them to the post they were attached to.
The way I read that, it looks like someone who happens upon this link:
would be automatically redirected to the post that picture it is attached to:
(The domain names are different due to use of a CDN).
That would be a fantastic feature. But if checking the "Redirect attachment URL's to parent post URL" option does not accomplish this, what does it do?