I’ve reviewed previous historical posts on anonymous posting, but they all refer to enabling something in the admin settings to allow anonymous posting at a certain trust level. I searched in the settings, but didn’t find this setting.
Our use case: professional site, want to allow people to post anonymously sometimes to ask a question / not be attributable back to their company.
I’m not sure if anonymous posting is enabled as standard on hosted customers, it might be worth checking:
That was last year though, and the position may have changed.
I’m out for the day but someone from the @team will help you out!
In the future you can always get support by emailing team@discourse.org
Done - you should see a message with more info on your 
Messages tab here on Meta.