This is similar but different from the /:activity format because the activity focuses on a single document, while the feed shows you all the things that happen in the whole site or section.

Maybe we should consider :activity/all or something instead.

Also note that the activity page has filters such as versions or citations. This could be handled with a query param but it is probably better to handle as part of the "panel param" because that is sometimes a ?panel= query param, and sometimes is located after the colon in the main path, when the feature is expected to appear in the main panel