For me its having a single instance that indexes all the communites to which all other instances can then pull that information from so when I go searching for communities the I’ll have access to every single one with needing to post the entire URL in the search bar
I fully understand wanting to restore things from a backup, but I don’t grasp how giving us the option to hard delete our own posts and comments would interfere with that in any way. Safest? Perhaps. A reasonable tradeoff for such safety? Not in my opinion.
As for your latter point, maybe that’s one of the drawbacks to federation that does not get discussed enough. However, I’d think there’d be some sort of solution to put more control of our data into the hands of the users.