You can’t force Google to show a specific URL as a sitelink in the SERPs
Sitelinks are additional results that are sometimes shown below a search result in Google.
John clarified that there are no meta tags or structured data that would force or recommend a specific URL to appear as a sitelink in the SERPs. Google’s systems try to figure out what is related or relevant when looking at a web page. He recommended having a good website structure, clear internal links, and to include clear titles to support sitelinks. There is no guarantee that it will yield a sitelink in the search results, but it helps Google to figure out what content is related and to choose a site link based on that information.
It’s not uncommon to see differences across schema validation tools
Users may see a difference in schema validation across tools. This is because the schema.org test is designed to validate all theoretical schemas, whereas the reports in Google Search Console and the Rich Results Test focus only on schema that can have a visible effect on Google search results. It could also be a simple case of the requirements being different across both tools; Google tends to be a little stricter on its requirements than schema.org. If the goal is simply for the marked-up content to appear in Google’s search features, it’s best to follow Google’s own guidelines.
Multiple instances of product structured data on one page is not recommended
Product structured data is designed to apply to the primary element on a page. A page with multiple products (such as a category page on an eCommerce website) essentially has no primary element, so product structured data is not recommended in these cases.
Breadcrumb structured data is not a replacement for standard internal linking
Even if a site is marked up with the relevant breadcrumb schema, internal linking continues to be a key focus. URLs included within structured data aren’t treated in the same way as regular internal links, so it’s still critical to link to the most important pages on your site within the HTML.
FAQ schema can be used on select questions
It’s possible to pick and choose which elements on a page to markup with structured data / schema. For example, not every question on an FAQ page needs to be marked up with schema if you see no value in doing so. (John does mention later on that for FAQ schema to be valid, the question must be visible on the page.)
It’s not possible to control which images appear in rich snippets
It seems that images are increasingly being used in the rich snippets shown in the SERPs, but there’s currently no way to tell Google which images are preferred for this purpose. The only option is to use the ‘noimageindex’ meta tag on images that you definitely don’t want to appear in snippets, but note that this particular tag will prevent those images from being indexed entirely.
Enhanced SERP content won’t show reviews from other sites
Enhanced search results (such as structured data included for SERP presentation) won’t appear if your reviews are being pulled from another site. This is true even if the relevant review schema is in place. Google treats reviews that have been aggregated from other sites slightly differently (it sees these essentially as testimonials, rather than reviews). So if the review didn’t appear on your site first, adding the relevant structured data is going to be a thankless task.
FAQ Content Should be Specific to Each Page
Content you provide in an FAQs section should be specific to each individual page and not copied across multiple pages.
Abuse of Schema Policy May Result in a Sitewide Manual Action for the Specific Type of Rich Result
Usually if you go against schema policy, a manual action for the specific type of rich result could be applied for the entire site until a reconsideration process is completed.