…n saving a Story.
Private tags would allow admins to create tags that only admins could use, and that regular users could not filter. The best example use case for this is an 'announements' tag for site announements that all users should see.
create a random rss_token for each user and append it to the rss urls. when adding the user-specific feed url to a feed reader, the user's tag filters will be applied before generating the rss view, giving the same list of stories that the user sees while logged in.