I believe this feature is popular across many social platforms - Follow. It means you get notified once the user you're following has new activity, post etc. I've seen some users here in Space SE (regardless of more or less rep) keep asking interesting questions and answering with quality answers.
Maybe there should have a feature similar as this; once the followed user has new activity, its followers would get notified. Perhaps through email, push the post they've interacted with (asked, answered or modified) or something else.
The "Active" tab is the one widely used I assume; in which the posts are sequenced by latest action carried out. Would a "follow" feature disrupts this and causes some questions to gain even less attention due to the preference settings?