alt Hacker NewsHmm, Word Online isn't what the article is about. I'm not sure if you've read the article, but it is about social apps — like Tumblr, Reddit, HN itself, etc.
I'm using file formats as a metaphor to explain how apps built on AT protocol work (lexicons are like "social file formats"), and what this way of building enables (interoperability between social apps by default).
I did read it. I think myself and other people are getting tripped up by the title and the filesystem-oriented argument. The article opens with an icon of a .doc file, so it's natural to think about MS Word, which these days is a social app via its collaboration features.