There's an eBook called "The Truth About HTML5" (http://www.truthabouthtml5.com/), whose entire premise is that the HTML5 sectioning elements are pointless. You can read the key chapter here: http://www.creativebloq.com/html5/truth-about-structuring-html5-page-9122842

I agree with the main point of your blog post, but I think the concept you're missing (through no fault of your own -- it is terribly/inconsistently explained) is that the purpose of the sectioning elements are to serve the "document outline". Once I understood that concept, the decisions about which elements to use became much clearer to me (although I don't even bother with the "article" or "main" elements because they don't make a lot of sense when you get down to it -- it's impossible to decipher the difference between an article and a section, and there's no need for main because everything that's not in a sectioning element is by default the "main" content).

All that being said, few people understand this stuff and every tutorial and explanation out there is somewhat contradictory, so I think at the end of the day none of this will matter in the grand scheme of things because nobody is using them the way they were intended (which I think is a failing of the spec, *not* a failing of web designers).

I think you sum it up best with your line "Right now they’re an extra layer of communication, except that no one is listening to that communication. And perhaps the inconsistent way we might use them means they aren’t communicating the same thing from site to site (assuming something is out there paying attention to the semantics)."

Thanks for the great blog post!

PS here's another great blog post by Nicolas Gallagher about the over-use and mis-use of the term "semantic" when talking about HTML: http://nicolasgallagher.com/about-html-semantics-front-end-architecture/