Most of the currently available ad-placement plugins for WordPress have options for placing ads between paragraphs of your posts. But unless you want to be adding shortcodes to all of your posts for ad placement, they give you no control of which paragraphs rthe ads will go between.
Until now…
The WordPress “More” line is the perfect logical place to put an ad inside your post.
You have already decided that this is the best point for a break in your post; that is why you placed the “More Line” there.