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Fragment of a discussion from Project:Support desk
That's an interesting question. You can always go to Special:RecentChanges and confine your results to the namespace 'Talk' (='Discussion'), which will show you the most recent changes that have been made to any page in this namespace.
If you like, it's also possible to transclude the contents of Special:RecentChanges and adjust the number of days or the number of changes shown per page (see this page here for further information), but there's nothing in the documentation that I could find about filtering the list on the basis of a particular namespace.
Hope that helps
