ceddit and others you have noted historically have broken for a variety of different reasons, and the others are are currently not functioning as the API they used was banned May 1st. Pushshift, which these services often used, had a mechanism to remove sensitive data you accidentally posted or otherwise wanted removed.

Archive.org is not searchable, not indexed in mainstream search engines. Also would be responsive to legal requests. It is hard to get a complete profile history on someone.

All of these external sources require a great deal of extra effort from someone to pry.

The concern to be aware of here isn't that it could be scraped, which yes it can. The concern is that it is duplicated by design, wide and broad, on a platform that somewhat functions as a single entity, the instant you hit submit.

People make mistakes. The Unabomber got caught by doxxing himself with a single phrasing of an idiom. Not complaining, simply saying "be very, very, very, very, very, very, very, very, very careful here"

And ultimately this comes down to different conceptions of privacy, sure, but one of these conceptions is suspiciously impossible to fix yet simultaneously deflective of the other, that other being directly beneficial to companies and any seeking to control mass populations.

Exactly. The privacy goal on federation is different. If people are educated, they can be safer.

You can't eat your cake and have it too.

Praise your local admins! And help them out by petitioning them to study their local laws and come up with proper policy and TOS statements.