But do you have to provide any information during such a signup that could be used to identify you in response to a valid legal warrant of some type? The "verification".
This depends on the exit node, so if you are experiencing this, we recommend trying another one. If it persists, contact us here so we can take a closer look: https://proton.me/support/contact
Experiencing what? To phrase my question differently: can someone show up on a Tor connection and make a new account without giving Proton any indication of who they are? So that in the case they abuse the account somehow, the only thing that Proton can do is just cancel the account?
Experiencing an additional verification step - sorry if we were unclear. Yes, you should be able to create a new account using our onion page or access our website via Tor browser. Additionally, you can create a Proton Mail account while connected to a no-logs VPN, which will also help protect your identity.