I actually quite like having Beehaw being proactive about their users' safety/ mental well-being.
I wound up making a second account on Lemmy.world so I can see what's going on in the larger Lemmy community, but I also appreciate being able to browse and post in a safer environment. I just wish the Lemmy back-end had more nuanced federation/ defederation options and better mod tools so I didn't have to make a second account to browse the extended Lemmy community.
I suspect powermods are more of a myth than reality, but I agree we should be concerned with any instance becoming the defacto site for Lemmy.
I think the best way to avoid this is already in motion (though slowly), which is to have smaller topic instances which house the topic in its entirety and don't have as many users (for example there is one for Star Trek and one for Android already). This way, regardless of your instance you still have access to the topic.
That's just my 2 cents, anyways.