I'd sort of roughly approached this technique with my own channel organization over time without thinking about it systematically, but this is a helpful crystallization of what I'd been trying to achieve. I'm glad this was posted.

Definitely agree with others that Slack needs a richer selection of notification mechanisms, both for new content in channels and for mentions. For mentions, there's no level between "I demand immediate attention from this person" and "the characters that make up this person's name happen to be in the text of my message."