I think "trying to make a thing that can work through rogue or stupid nodes" is just prohibitively harder than "work on making nodes more reliable" (which I absolutely grant is extremely hard.)
Nothing. You must always have this in mind when posting online: It's impossible to ensure that data is deleted and gone forever.
Taking this idea further -- this is the sort of thing that really makes me consider whether or not ATProto might be literally the worst idea in all of social media.
Which is to say "can track you just as intrusively as any private service, but now your history is cryptographically signable and even EASIER to share and move everywhere"
Didn't even took a year to see where the texts are still readable today.