Google Does Not Use W3C Validation
Google does not use W3C validation for web search, so you do not need to worry if your pages have any validation errors, however the validator is a great way to make sure your pages display properly with other systems like screen readers.
Inform Google of Efforts Made to Clean Up & Remove Pages Under Manual Review
If you have a lot of pages that are under manual review and you delete a lot of those as an effort to clean them up, then John would recommend mentioning this in your reconsideration request. This shows that you have taken significant steps to clean up any pages which are under review.
There Are No Issues With Having More Than One Author For a Post
Google has no issues with having more than one author attributed on a post.
Site Quality Doesn’t Impact Whether Sitelinks Shown in SERPs
Google will display sitelinks in search results when it makes sense for the query a user is searching for. It isn’t determined by the quality of a website.
No Need to Optimize Websites Specifically for Quality Raters
You don’t need to specifically optimize sites to be accessible for Google Quality Raters because they won’t be reviewing individual sites. The Quality Raters are simply given a list of SERPs with and without an algorithm change, and they then decide which set of results is better.
Don’t Focus on tf-idf to Optimize Pages as Search Algorithms Are Much More Complex Now
John recommends not focusing on tf-idf because it is a very old metric and algorithms have evolved a lot since then. Using tf-idf to squeeze words into your pages is unlikely to be useful and is a short-sighted approach.
Google Does Not Use Domain Authority in its Search Algorithms
Google does not use Domain Authority to rank pages in its search results, as it is a third-party metric.
Displaying Expertise on a Topic Plays a Role in Rankings
There is no quick fix for improving a site or author’s expertise on a subject, however, this is a factor that feeds into rankings. It takes time to build a presence as an authority on a topic.
Rewrite Low-quality Pages or Combine Them With Other Relevant Pages
Google’s quality team avoids telling website owners to delete pages, and instead promotes the idea of rewriting low-quality pages or combining them with and redirecting them to relevant, higher-quality pages.