@aleksei if you change the setting I said then new users will by default automatically be notified when replies are made to any topic they post. There's a different setting for if you want to be notified about replied to a topic you replied to.
Again: you can configure the defaults for user settings in the ACP. New users will automatically be assigned the settings you select there.
There's no way to make people be notified about every reply to every topic even if it isn't their topic or they didn't reply to it.
