yeah i think communities being different from each other even if they're discussing the same subjects is a good point. this same idea probably applies to the way people interact in other instances or what communities grow on there.
reminds me of going between different forums and boards many years ago when that was something you had to do to see discussion on specific topics before most online activity was grouped into sites like twitter, reddit, facebook, etc.
i think my concern comes from the idea that large instances could set the pace for how other instances operate. if admins for lemmy.world wanted to enact certain policies the fact that they have the largest userbase would encourage other instances to fall in line since they wouldn't want to defederate from the largest instance.
i should also admit that i'm not completely aware of the process through which instances federate and defederate from each other. i assume it's up to the discretion of the admins of each instance, and then once many begin to federate together the admins of each have their say on who can be included, with defederating occuring if there is no longer alignment between an instance and it's federation. correct me if i'm wrong, but if this is correct, large instances like lemmy.world would hold an unequal share of bargaining power in these circumstances.