Which is exactly why a broad brainstorming topic can work quite well with a bit of guidance and teaching ppl how to manage and encouraging a topic that will spawn new sub topics with SoGs and SoPs helping to make it work.
New topic branch? The post with the link can be highlighted with Staff Notice for example…Op Statement can be editted to identify where to discuss a specific element…Etc…
It is about removing barriers not imposing them.
@simon mentioned the 30 day reset replies topics. Reset Category in a free for all motive can work as well. Start a topic to fletch out an idea. Just before 30 days end. Copy key points modify op statement start a new 30 day brainstorm. Just an idea of sorts.
Which reminds me iirc there was maybe not long ago a plugin adding a form of topic threading. Will look and see if can find.it. 