It's actually fairly simple. If a user notices a post in their feed from an account they don't follow, they can simply click or tap on the three dot icon located in the upper right-hand corner of the specific post. This will open a drop-down menu.
However, if the post is an ad, this menu provides additional options. ... "Not interested in this ad," ... "Report ad" ... "Why this ad?"
You bet your ass that they are going to get rid of those options.