Otherwise, probably one of if not the biggest experiments being run on the #threadiverse right now is how groups/communities run when decentralised at substantial scale.
Spread over instances will create more duplication/parallel communities than on Reddit, but will this be a good thing for diversity, or, a turn off with similar engagement issues some twitter migrants found here.
ATM, my feeling is, provided the UX is good enough, that it will be a pleasant balance.