This doesn't help. Now the implementation depends on another component correctly reading some global state, an undeclared dependency. If I'm reading the upvote

This doesn't help. Now the implementation depends on another component correctly reading some global state, an undeclared dependency. If I'm reading the upvote button I have no idea that it uses a notification-bar. If I'm reading the notification-bar I have no idea what it's for or who uses it.