Restoring missing Newsfeed-related Email notifications on user profiles

I'm exploring the use of Community Sites in our production SPO tenant.  In other tenants I have worked with (including our DEV and CERT tenants), user profiles always had an email notification checkbox to disable the sending email notifications when someone replied to the a Community discussion thread that I created.  However, in my production tenant, this is not the case.  I have made sure that our social media settings specify SharePoint Newsfeed rather than Yammer (it was set at Yammer but I changes that setting more than 48 hours ago and the email notifications list still does not have Community Site-related values in any profile I looked at).

 

Does anyone know what other settings need to be changed to restore these email notification settings?