Key to trick was to have bucket named "xrpc" and store a file there: https://s3.amazonaws.com/xrpc/com.atproto.identity.resolveHa...
There is also another funny thing in the image, the user posting about is sending one from "retr0-id.translate.goog", which is odd. Somehow he has got https://retr0-id.translate.goog/xrpc/com.atproto.identity.re... to redirect to his page, and gotten that handle as well.
I myself have had an account for like a month now, but only started really using it a week ago, because that calculus changed for me, personally.
Like, it's not even possible to truly delete posts at the moment. This all needs to be treated as a playground until things mature.
This isn't even the first "scandal" related to this feature already!!!! There is another hole in what currently exists that allowed someone to temporarily impersonate a Japanese magazine a few weeks back.
A PR of "Change external domain validation to use .well-known (or DNS01, etc)" is not a "bugfix"
I'm not going to speak for the commenter you're replying to, but I don't think anyone here is talking about the standards-compliant, DNS-based domain verification system. I think we're all talking about the non-standards-compliant, /xrpc/-path verification.