not sure if this has been thought about before or if some other flavour of activitypub does it this way but i wonder if "CW"s would be better utilised if they were treated as email subject line and only defaulted to closed if a word in your custom blacklist appeared on it
i think that would push people to describe the content of posts much more if they're not implied to be opt-in, though this would also need a defacto "standardisation" of subjects, for example "uspol" vs "us politics"
my thought is that right now it's all or nothing in terms of when you use a "CW" your post will be hidden
if instead people can choose that only certain topics are default hidden and the rest aren't, then there's a lot less "but i don't want to hide this" stigma against using a subject line