Yeah this is something that too few people get about the Fediverse. Because it's decentralised and sends your data to many independent servers by default, it's in fact even harder to scrub what you post off the internet than a centralised platform. Even if your current instance goes down, other federated instances will still have a lot of the original posts and comments. You can never be certain that all instances have deleted your post or comment because they can simply not comply with the signal from your home instance asking them to delete it, or have defederated between you making the post and you deleting it so it never gets the deletion signal. Plus, you have zero way of knowing if any instance still stores the original content on their servers or in backups even after you've both edited a post blank to remove the text and deleted it.

This is certainly a double edged sword. On one hand, it makes information that was intended to be public more accessible by the public. On the other hand, it does run up against the "right to be forgotten" doctrine, and does have very real privacy implications. Lemmy is better for privacy in terms of not tracking your browser and not having ads, but worse for privacy in that anything you post can't really be deleted.

But more than anything, it's a reason to think before you post because you likely won't be able to take it back.