I believe more and more people will escape to lemmy sooner or later, and I already see 3 different communities for the same thing (selfhosted) here on lemmy. Time will tell which one will be the most active, but lets assume all of them will be equally active and the desire emerges to combine the two communities about the same thing, is that something possible or intended to be possible with federated services?
We deal with that in Reddit too though. I see your point but if people are subscribing based on user count then eventually the best community will win I guess?