Taking some liberties with the situation, behavior, impact framework:
Today I found myself thinking: “I had forgotten that you can always ask @deeplow to split a topic if you notice that questions appear which sound interesting but are not strictly on-topic (may not be of interest of everybody in the thread), next time I’ll call that out early.” Trying to keep the distinction clear while, in practice, creating sub-threads is without doubt a bad idea in hindsight.
As someone who has recently joined the forum, I think it wouldn’t hurt reminding that the above is an option from time to time.
At a personal level, I think such a reminder would make after-the-fact observations of “it’s too late now, people won’t join the conversation anymore” feel less unfair, and the forum feel more inclusive to newcomers. After all, structured conversation is a skill and requires practice too. (That was not a quote by the way, only the retranscription of my perception.)
I hope this makes sense and helps increasing the number of collaborative conversations on the forum!