I think Matthew Green's point was more that requesting a public key leaks your intent to communicate with someone—the metadata, if you will—to an untrusted thir

I think Matthew Green's point was more that requesting a public key leaks your intent to communicate with someone—the metadata, if you will—to an untrusted third-party. Of course, e-mail headers, including From and To, must necessarily transit as cleartext, even when e-mail bodies are protected by PGP. The keyserver should perhaps be the least of Matthew's concern.