If a person subscribes to a MSI notification through Salesforce, their is no way for a SFDC admin, Marketo admin, or Marketo support to unsubscribe that person from the notification, such as:
You are subscribed to Marketo Sales Insight Interesting Moment for "Type: Registered"\n\n
When a Salesperson clicks this accidently, they can get 100's of emails, which can block our Marketo notifications, lead to spam filter issues, etc.
The only way this can be unsubscribed is from the email link itself, and by that specific user who clicked the notification icon.
Please add to roadmap to give a way for Marketo admins to clear these subscriptions.
Marketo Support confirmed this old ask article was accurate - 0 way to clear these out:
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