Here's a quick memory jogger for me: If you try to validate the AMP versions of blog pages, you may get this error from Google:
Invalid URL for HTML attribute 'href' in tag 'a'. What does it actually mean?
not difficult to make mistakes in how you set up your site that lead to difficult to diagnose failures in the WYSIWYG editor. I came across one such issue recently that seemed like just the sort of thing Google needs to know about to save future developers (and probably Future Me as well) from the pain of debugging it.
As time goes on, something I've noticed is that as Sitecore evolves it is taking a greater reliance on search integration – making things like Solr ever more important. And that leads to an exciting new set of issues you come across if, for some reason, your search service is not available.
I wasted some perfectly good development time recently when some of my renderings vanished from published pages, thanks to this.