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For IP logs is it only the admin of the instance account is created on that could view it? Or is it also the mods on the instance? Can every other admin or mod from another instance view the information?

What about for saves and messages?

By default admins of each instance can access everything from accounts that were created there, but unsure of the access available to everyone else. Would be fun to learn what federation with other instances and participating in them reveals to the admins/mods of those other instances.