Here's an example schema.

Users

    {
      _id:string //doubles for user's name
      password: {
        hash:string
        salt:string
      }
      website:string
      bio:string
      following:array of {
        username:string
        articles:boolean
        comments:boolean
      }
    }

Articles

    {
      _id:ObjectID //auto id
      title:string
      contents:string
      owner:string //references Users
      tags:array of strings //no reference, tags are either unfiltered or selected from a global tag list. 
    }

Comments

    {
      _id:ObjectID //auto id
      contents:string
      owner:string //references Users
      root:ObjectID //references Articles instead of Comments
      parents:array of ObjectIDs //using materialized path for threading of comments
    }

Config

    {
      _id:string
      value:? //untyped can store anything in json format
    }

Note: The references are defined entirely in software, the database is not aware of them.