If I understand Lemmy correctly, you can create duplicate communities on different instances. Isn’t this kinda counter productive because this may lead to less user interaction in those communities, because the user base gets split up between competing communities.
Is there a way to fight this division of the (small) userbase or is this effect even desired because it leads to more tight knit communities on the different instances?
They aren’t competing. As a user you should strive to follow ALL the comms with a similar topic, why limit yourself to the currently most popular one?