Very fair point, and all perfect examples of the value of circumstantial censorship.
To Aether’s credit: something can’t be both ephemeral and unremovable; being ephemeral suggests that it will be removed automatically given enough time. To my understanding: the moderation policy on Aether prevents users from downloading content that moderators have hidden. It is only if a user goes out of their way to view hidden content that they risk exposure to it.
If federation from Aether to Lemmy were technically possible, surely it would be within the capabilities of Lemmy to only pull and display data that the moderators of an Aether instance deem appropriate. It would of course be up to any Lemmy server host whether they accept the federation, and if they feel the need to blacklist any Aether communities.