The design of email means there is an argument for the legal system that gmail is a very very popular post office. That email is a system wherein users have disparate storage areas for receiving/archiving emails, and gmail is one of many organizations that offers users the service of managing their individualized storage area on their behalf.
In the service that is email, there is nothing inherently special about gmail. In the service that is discord, discord is discord.
IRC enables Text & Attachments in text form (ie links)
Email Enables Attachments in visual (html emails)
Discord Enables Voice, Text and Attachments (Asynchronous sockets)
That's all it is. Present a Video, Picture, Voice to your visitor and you've got a new product. Just as facebook,twitter,myspace.
Assuming all this is correct, if a GMail user requests their account to be deleted, Google should delete that data.