Back in August '15 I posted a thread called New kind of annoying pop up ads. It was similar to what I'm seeing here, except the ads would appear and disappear quickly, displacing the text of the post, making it hard to read. Soon after I posted the thread, the problem went away; I think the forum host fixed it somehow.
I suspect advertisers must have specialists who are tasked with making advertising as intrusive and obnoxious as possible.
Tom