I am struggling to find any resource on what a staged user is, what makes them different from a regular user and how this is beneficial to the community, the admin or the stages user themselves.
What is/are staged users? 
You can find more about other user states here:
Hi Maja,
I did read this page, but it didn’t make much sense to me regarding the applications of staged users.
Am I correct in assuming you don’t set up a stage user?
A very oversimplified explanation of a staged user:
A user that probably exists in real life but has never registered to your site but has somehow managed to create a topic (usually through the email in option)
The only use case for a staged user that I’m aware of is when someone has an email ID which is set up in discourse to allow topics in email and allowed the creation of a staged user account for any emails that do not have an account associated with discourse.
The benefit it has is that people who want to create a topic but don’t have an account can still send in their topics without going through the process of registering an account and then creating a topic.
Use case 1: anonymous posting from throwaway email (not sure how it’ll work but still)
Use case 2: creating a support email and using discourse to keep track of it (we use it)
Use case 3: Mailing list (again, Not sure)
If the enable staged users and the email in Site Settings are enabled on your forum, staged users are created automatically when they send an email to create a topic on your forum. For details about the email in Site Setting, see: Configure incoming email to create new topics or group messages.
On the meta forum, the Discourse team has enabled incoming emails to be posted a group. When emails are sent to our group’s incoming email address, staged users are created.
The benefit of this is that it allows the whole Discourse team to participate in answering support requests directly from Discourse. This lets us use Discourse tools to manage support requests - we can assign tasks to members of the team, tag messages to allow us to sort them later, search messages with the in:private search filter, communicate privately within messages if we have questions that need to be answered by another team member… It’s a huge improvement over trying to handle communication through an email client.
我们大量使用“临时用户”（Staged Users），但方式可能与这里提到的不同……
我们会向新的潜在用户发送私信（PM），并为此邮箱地址创建临时用户。随后，我们可以将私信转换为话题，这样任何数量的普通用户都可以通过回复该话题与该临时用户进行互动。
不过，我们并不喜欢 Discourse 在普通话题或私信的回复中为任何抄送（CC）方自动创建临时用户的行为。这非常令人头疼。换句话说：主动创建临时用户是好的，被动创建则不好。
问题：我们该如何关闭该行为，同时保留我们发送并创建临时用户的能力？关闭 enable staged users 选项能做到这一点吗？
我们目前还没有达到这种保真度，这需要插件。
为了明确起见，我理解您的意思是，关闭“启用分阶段用户”选项将阻止我们在私信中与或非用户邮箱地址进行发送和接收。
我认为你可以从消息中心进行操作？
抱歉，我尝试像在消息中添加用户名一样添加电子邮件地址，但它不被接受。
我应该如何添加电子邮件地址？
我现在无法访问该网站，但似乎有一个设置允许您在 PM 窗口中添加电子邮件地址。