I’ve long wanted more of this because I think we lose a lot of value by straying off here and there as people jump in without regard to the focus in an OP.
Those keen to explore more widely would learn to “reply on another topic”, so those discussions can still go on. In general I don’t think moderators want the extra work of this which I can understand. Cleaning up topics isn’t a favourite, you get flack for it etc.
EDIT: how about trialling an on-topic-only tag on which mods apply a strict please stay on topic policy and move infringing stuff without question (referring to guidelines). The original poster gets to apply the tag, or not. To begin we could ask original posters to append some boilerplate explaining this whenever they apply the tag.
EDIT2: @david-beinn I added an on-topic-only tag to your brainstorming topic and suggest adding the following boilerplate to the bottom of the OP:
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Please stay on topic in replies
This is tagged on-topic-only so please stay on topic in your replies, and if you want to spin off a wider discussion please replay on a new topic by clicking the ‘link’ icon (a two link chain) under a post and choosing +New Topic.
This is an experiment, so let’s see how it goes. Thank you!