I am still having issues with Global posts. I copied the link address from the supposed ‘duplicated listing’ and discovered that they are pointing to different locations
https://blogs.caryacademy.org/tags-2015-16/2015/09/24/led-it-up-29/ - this is the global repository of tagged blogs
https://blogs.caryacademy.org/chasec773/2015/09/24/led-it-up/ - this is the student’s blog page
Based upon this information it is safe to say that the listing is properly reporting two different pages. The two pages are presented differently which I assume must be indicative of the templates applied to those pages/blogs.
There are clearly two different blogs with unique URLs. The Tags page must report them as such.
Old ticket https://premium.wpmudev.org/forums/topic/duplicate-posts-listed-on-global-tag-pages#post-1013657
JetPack is off as well as other pugins.