

I still dont think you’re comparing apples to apples here.
A physical payment for the thing you linked (I dont use posteo but they seem to use the same cash+nonce system everyone else does) consists of a sealed addressed envelope with the bills and a number used once (nonce) at the recipient in order to associate receipt with account. The nonce is not saved or recorded.
So a surveilling party could possibly perform in depth inspection of every letter going to the service they’re trying to surveil, record all the payments and nonces, cross reference the mailing location of the individual letters (idk of any post service that bins them according to location of origin but I’ll go with your description!) with public camera footage and make a positive id for all the people who mailed the letters and they still don’t have the ability to associate payment/person/letter/nonce with a particular account because the nonce isn’t retained.
They’d just know you sent a letter containing money and a code to a service.
Again, what I described is a type of investigation that is extremely expensive and requires exacting precision at every step in order to not make an error that would make the evidence inadmissible.
They’d have to have infiltrated the recipient at the time and place of associating account with nonce and if that’s the case it doesn’t matter if you’re using the monero jetpack/ninja climb or the physical letter walk across the gymnastics mat t-posing method because the other end of the mat is jail.
But let’s look at it from the other direction, they’re not trying to remove privacy and anonymity in general, they’re specifically trying to get you:
You are observed through your open window from the cleaning service van across the street. When you leave to mail your letter, which contains unique microscopic markings and fiber identifiers cross referenced to the s/n of envelope boxes you were recorded on cctv purchasing at the drug store last week, the van radios a follow car around the corner that appears to be a bunch of hoodlums who slow to a crawl and yell out their car window, berating and denigrating you. You don’t respond, though their yelling distracts you from the pebble in your shoe and the traffic cameras get a good id on you through gait recognition.
The follow car bumps into a fire hydrant and you round the corner and enter the restaurant, where the server seems to be looking at you and texting constantly. Your grilled cheese has melted chocolate in it with the unique mushroomy taste of senna. You catch the host and bartender running your change back to the office and hear the sound of a scanner and notice the shifting white light coming from behind the open door.
You put part of your change in the envelope with the nonce you wrote using your non dominant hand and lick it to seal the flap, activating dozens of moisture sensitive polymer capsules to absorb and preserve the trace genetic material left behind for later analysis. Outside the restaurant, you drop the letter in the mailbox and head home. The restaurants host radios when you round the corner and a flower seller with dark sunglasses, an earpiece and a conservative suit on under their apron rolls their cart down to the mailbox, unlocks it and picks out your letter.
They know that you sent a letter with money and a code to some address. If they allow it to continue on its way then they can’t associate it with a particular account because the code isn’t retained after use.



Gotta excercise the ol creative muscles somehow. Thanks for putting up with it!
I think what you just said is our breakdown. Neither cryptocurrency, cryptography (in its d-h or one time code permutation) or any other technology removes the requirement that you trust the other party both to perform their side of the process and to not betray you.
It’s important to not go down that route because if you can’t ever trust then you can’t believe you can ever have privacy or anonymity except when you completely retreat from all communication or interaction both electronically and physically.
Remember that the problem cryptocurrency solves is the credit card clearing problem, not the problem of trusting your counterpart.
Also your proton example might be the one where some ding dong used their out of the box (no adp) icloud email as the recovery for proton and the cops got the icloud through a logged in device and recovered the proton account using it as opposed to forced ip logging but I might be mistaken.