Dominik, the updates do include changes in personal spaces the user has permission to see. Each user is a space admin of their own personal space and can restrict the permissions to limit who would be able to see the content and hence receive daily updates on the personal space.
Please see details on Email Notifications
The Daily updates email contains:
Pages and blog posts that are added, edited or deleted.
Comments on a page or blog post that are added, edited or deleted.
Updates by users who have changed their personal profile.
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