Just an update on this one -
You could create several users with nonsense email addresses and then activate them from their admin/user page. As you don’t actually need to send them an email you also don’t need to validate their email either.
It is possible to impersonate system and Discobot, but you would need to be a ‘sysadmin’ admin for that (ie. you need to have your account email in the DISCOURSE_DEVELOPER_EMAILS section of your app.yml).