But, whoever’s doing the redacting sees the original right? What prevents the redactor from saying, “here’s what the document really said.” Or “here’s who’s in the image, I saw it before I redacted it?”

The idea of spending the rest of their life in prison is what stops them

Part of the law mandates that all redactions will be listed for Congress within 15 days.

I’d guess a first pass is done automatically? Eg if a page mentions eg Trump, just redact that whole page/paragraph/etc. So the people who have done the closer reading to redact further probably don’t actually know the scale of what was already redacted. Just a guess though.

People who they think will do this don't get to be redactors. It's all about power and relationships, not technology.

Given how MTG went completely silent despite her high profile platform, I'm guessing the civil (or at this point, royal) servants don't want their families harmed.

That’s a good point. I would imagine they break it up into pieces - in a reCAPTCHA sorta way - and any given person sees a sentence or a piece of a sentence.

An alternative would be to strip out all obvious known words and only leave unknowns (i.e., names) and then have those fragments reviewed (in a reCAPTCHA sorta way).

Finally, for images, cover all faces and the one by one decide which should remain covered and which should not.

LOTS of work but there are workflows to mitigate the ability for reviewers to connect more than they should.