Oh i'm sure it's not intentional....

What I would suggest doing is either of these:
*Inline the add after the top post of each page, many website do like this, anyone browsing past the OP will still see the add and it prevents this.
*Another option would be to move the "view last unread" from the header of the top post to somewhere near the top banner. That way at least you can aim for it without the goal posts moving

Thank you for listening