With reddit we mostly had a single subreddit for a given topic, for the sake of the question let’s use gaming. If there were alternative subreddits dedicated to the same topic, they had names that gave that away. Do you think Lemmy will lead to more segmentation, and more information bubbles seeing as we now can have gaming@x and gaming@y without a obvious way to see which community is the “default” one? Will it be a good thing, as you can find a community that suits your preferences better, or will it stifle discussion?
That is indeed a problem that can happen, as I saw other people commenting about this issue.
I am somewhat optimistic that people will gravitate towards the bigger communities, making them the unofficial defaults. But there is the risk of people being split into lots of smaller ones, which may cause them to die due to low traction.