Instead the microblog view is a view of the comments in all the magazines without being organised under posts.
No, that's absolutely not the case. From the microblog feed, I'm able to find my own posts from Calckey and PixelFed (e.g. https://kbin.social/u/@[email protected]), neither of which have touched or in any way interacted with n a kbin magazine.
You can follow users on kbin, but AFAICT you don't have home or local timelines, only federated/global. Instead, these stream of posts that are not addressed to a Group actor can be mined for hashtags by magazines, and those posts with matching tags get shown in a magazine's Microblog tab. Any posts that are untagged, or which cannot be assigned to at least one magazine, get dumped into m/random's Microblog feed.
Threads are specifically addressed the Group Actors. Comments belong to whatever they replied to. Microblog posts neither address a Group Actor nor are in reply to a thread or thread comment, and so are fundamentally detached from the core threadiverse ecosystem.