Here is site history. Old domain 10 years had one seo work on it back in the day directories were the thing. Looking at his profile I can't find anything jump out. Old site as I said has a resource page with some links. None of them are in an anchor text, all good sites most of them old. When I say old over 8 years.
The only thing I can see were this site could trigger a email on the Google Webmaster Tools notice of detected unnatural links.
He has a page on his blog to be specific were he has in text "Advertisements Add your Link here" and some of the partners added from the resource page. He was trying to increase revenue anyway he could. This was added years ago like 5 or more so really nothing new. I guess the tweek has to pick up on terms within the site and if this has a links page could cause the email.
Nothing else there took some time looking over the site. The blog is really a good one full of good information for the user, he hasn't lost positions so far. Nothing else there. Like I said in the other post he hasn't had any SEO work done on the site in years, no new links added in years on the links page. All of the outgoing links are quality sites. Got to be the Advertising and add links on the same page to cause this.
No anchor links as I said, no bad links, profile is fine nothing jumps out he has affilates but these are linked differently so they don't show up in profile.
I feel it is this one page with the text and partners that triggered the email all I can find.
As Paul would say "Now You Have The Rest Of The Story Good Day"