Via /r/Bitcoin: Blockchain.info becomes the second website (after Facebook) to have been issued an HTTPS certificate by DigiCert for their .onion address.
Unless I completely misunderstand how Tor works, this means the blockchain.info MITM attacks via compromised exit nodes would be completely mitigated.
That's true regardless of the certificate. Communication to onions are encrypted whether it's http or https. That extra 's' only adds encryption on top of encryption, which isn't harmful afaik but doesn't change much.
Imagine what would happen if anyone could run an exit node and mitm your communications with agora or evo.