"doesn't matter"

Did you ever stop to wonder what Google search is actually doing? You talk about them trying to defeat "blackhat SEO". They don't care what colour hat anybody is wearing. They want to direct users to what they were looking for. No matter how white your hat is, if the other guy has what the user actually wants, Google's goal is to direct them to that site, not yours.

That's why SEO is so sad, ultimately - the best optimisation "trick" is to provide the content people were actually looking for, that's why for many words and phrases the top hit is a Wikipedia page about that thing.

Rather than obsessing over the use of metadata for self-description to drive search traffic, like an SEO, try to think about all the other machines using the web. Most robots are not indexing for a search engine, and most non-human agents reading a web page aren't robots (they are instead various plug-ins and proxies "eavesdropping" on pages read by humans). All of these systems can benefit from metadata, even though it doesn't help SEO. Because, SEO _doesn't matter_, it's the seagulls fighting over the scraps thrown from the ship. Seems important to the seagulls no doubt, but the ship doesn't exist to feed seagulls.