About baltic tu "thou"
Fragment of a discussion from User talk:Rua
Why slavic form is seperately in the section *tūˀ (https://en.wiktionary.org/wiki/Reconstruction:Proto-Indo-European/t%C3%BAh%E2%82%82), Balto-Slavic: *tūˀ
Slavic: *ty (see there for further descendants)
but all forms together are presented in https://en.wiktionary.org/wiki/Reconstruction:Proto-Balto-Slavic/t%C5%AB%CB%80
Latvian: tu Lithuanian: tù Old Prussian: tou Slavic: *ty
Slavic form is much more important?
It's because the Slavic page also lists descendants, so people can get to it more easily. If you really want, you can use {{desctree}}
on the Proto-Indo-European page.