There's also this from the CPS:
Subscribers can revoke certificates belonging to their accounts via the ACME API if they can sign the revocation request with the associated account private key. No other information is required in such cases.
Now, that's not saying anything about revocation reason, but it seems really weird to me that a CA would accept a revocation request, but not for the reason of a compromised key (which is the main reason one would want to be sure to revoke).