When making a forum, there will be an option that allows u to subscribe ur own forum ur creating or not. There will also be the same option at every other ppl's forum, to subscribe it or not. There will be also another option to allow the website to send u through email about the replies from other ppl to ur/ppl's forum.
Inspired this idea by Mineplex forum.
Drupal doesn't allow this. For this to happen, we'd need a whole new forum system.