x-sign-this: is potentially dangerous and should not be enabled by default
x-sign-this: implements an automated notary, which list operators may not wish to expose. In particular, the list key may be abused to sign a malicious or misleading statement, or a request body that could be passed on to another automated system that uses signatures as an authentication mechanism. While this feature is useful, it should only be enabled by admins who understand the consequences, and should never be enabled by default.