I also find your introductory post to the subject (https://www.joshcanhelp.com/testable-documentation-intro/) really neat !

The docco spike is quite cool, sounds a bit like inlined Javadoc on steroid to me, as you mention in your final thoughts it could look great for direct source code documentation. Not sure about the immediate readability with all these comments though, I think there is a hard balance to find between wanting documented code/samples and not wating documentation concerns to 'invade' your codebase too much (something you kinda pointed out too).