I'd need to think about it deeply, but at a first sight, nanoblogging would be a simple text (like the original twtxt spec, aimed for TUIs), and microblogging (like Twitter was a few years ago), would be about sharing texts, images, videos, GIFs, links, and perhaps Markdown styling.

Why? You have shorter messages than in a blog, but you may add almost anything you could do in a blog. Buuut... who knows?