If I understand you correctly you want to filter a feed on specific criteria (e.g. topic). Even if the feed publishes a lot of other content, you want to know the ratio of bookmarked content based of the filtered feed, ignoring the other content.

It's a great point, and helps me extend the feature and make Lighthouse better. So, thank you!

Lighthouse actually has that data. It supports rules, and tracks if a rule made an action (e.g. archive an article). So basically the ratio could ignore all articles that were automatically archived by rules.

I need to think more about how the UX of it should be, but it's a good next step for the feature.