Google has updated their quality raters guidelines on July 27, 2017. Previously it was updated on May 11, 2017 with some smaller changes and then the bigger changes on March 14, 2017 with the offensive, upsetting, inaccurate and hateful web pages clarification.
Jennifer Slegg dug deep into the changes.
This new update touches on several points but the big items are conspiracy theory web sites and non-English results and locales.
Conspiracy Theory Content In the Document
Presents unsubstantiated conspiracy theories as if the information were factual.
The MC on this page contains factually unsupported theories related to the Vatican's knowledge of the planet Nibiru, the existence of aliens, and upcoming world events. Although various Vatican officials and scientists are quoted in the article, the quotations do not support the article's claims, and in some cases do not seem to come from the person quoted. The Nibiru cataclysm and related events have also been thoroughly debunked by authoritative sources ( Reference 1 , Reference 2 ). The demonstrably inaccurate content on this page can misinform users.
Pages that directly contradict well established historical facts (e.g., unsubstantiated conspiracy theories), unless the query clearly indicates the user is seeking an alternative viewpoint.
A nonsatirical webpage or website presents unsubstantiated conspiracy theories or hoaxes as if the information were factual.
Non-English Sections
However, rating can be more difficult when the query includes English names, words, etc., or when it’s unclear whether English results would be satisfying for a particular query. Please use your judgment and knowledge of your locale to determine the appropriate rating.
Important: Please keep in mind that every locale will have unique considerations regarding the number and variety of languages (such as official languages, regional languages, local dialects, etc.), writing systems, and keyboard input languages commonly in use. While this guideline may not include examples for your locale, it is important that you represent users in your task location and culture in order to interpret the query and rate results. When in doubt, please assume that users would prefer results in the task language unless the query clearly indicates otherwise.
And much more.
Forum discussion at Twitter and WebmasterWorld.