In my reading the point of the post is that it's important to have a record of the important things (like why did we decide to do X, or to do it in this specific way), and that putting such discussion in the same context as things that aren't important to record makes it very hard to filter out the important bits later on if needed.
So they advocate for putting the important information in a separate context, that also allows for more thoughtful conversations.
That's a plausible interpretation, but the notion that "important=anything that matters for longer than 1 day" still makes no sense to me. And I also disagree that it's a priori important to have a record of important things. It's nearly tautological, and even if it weren't, there are some strong embedded assumptions about how to build software that at best need close examination.
So they advocate for putting the important information in a separate context, that also allows for more thoughtful conversations.