try the shared inbox for update deliveries

activity.go

@@ -1366,9 +1366,15 @@ func honkworldwide(user *WhatAbout, honk *Honk) {
 			}
 		}
 		for _, f := range getbacktracks(honk.XID) {
+			var box *Box
+			ok := boxofboxes.Get(f, &box)
+			if ok && box.Shared != "" {
+				rcpts["%"+box.Shared] = true
+			} else {
 				rcpts[f] = true
 			}
 		}
+	}
 	for a := range rcpts {
 		go deliverate(0, user.ID, a, msg)
 	}