I could see this being used in a similar way to user agents (sometimes helpful when working on bugs and fixing them on minor platforms!), but I'm really struggling to see the overall value-add here.
I get the politics aspect of it (I think...), but what's the new technical thing being added here?
[0]: https://github.com/RupertBenWiser/Web-Environment-Integrity/...
So you can't fake that unless you have the third party's private key.
If course the question is then, how does the attestation third party ensure you are sending it real information? I've not bothered to read the proposal because I don't care, but I suspect it will require client-side plugins/libraries etc snooping on what is going on kinda like an antivirus thing snoops on things going on.
The WEI standard does not prescribe this, as far as I can tell. One way to do this would be to use something like Secure Boot (broadly speaking), which can make "independent" measurements of what is being executed and sign that with a private key that never leaves (something like) a TPM.
I Pissed Off Every Cheater in TF2 (Data Breach Gone Wrong) | https://www.youtube.com/watch?v=LVgk5t64cRs
Creating a Third-party Client to Auto-kick Cheaters and Bots from TF2 (Part 1/3) | https://www.youtube.com/watch?v=EPsWjdkyoPo
Basically cheaters don't seem to want just a one off high like a classic troll out for havoc, they want a reputation of being better than they are for an extended ego trip. Their choice will soon be either restraining themselves to becoming very subtle, or keep having to make new accounts.
So the data isn't there at all - it's not just hidden away behind some JavaScript