Notifications: One-stop shop
There is a system notifications page already at /notifications/system, but it is only available in the New Members feed? And you have to click each notif to read the context, and it jumps around.
We could repurpose this page (or make an addon to do the same) to show more of the context inline, which would make it easier to catch up on what's happened. Even just a little snippet like Tumblr uses: "X has replied to your post: 'start of post text ...' " would probably be enough.