There's a third tier, something like "approved submitters." Some subs, especially smaller ones, would randomly add users to the list based on some criteria. The

There's a third tier, something like "approved submitters." Some subs, especially smaller ones, would randomly add users to the list based on some criteria. These people would be able to browse private subs as well. There's a way to see what subs you've been added to as an approved submitter, somewhere on old.Reddit under the subreddits page