I'm not sure privacy violation is necessarily the right term to help people understand why long-term non repudiation is an undesirable property for some people.
It comes down to if a third party gets access to your emails (e.g. through a server compromise), should they be able to prove to a fourth party that the emails are legitimately yours, vs completely faked? Non repudiation through strong DKIM keys enables this.
Example: Third party is a ransomware gang who releases your emails because you didn't pay a ransom after your email server was compromised. Fourth party is a journalist who doesn't trust the ransomware gang, but also wants to publish juicy stories about your company if there is one, but doesn't want to risk their reputation / a defamation case if the ransomware gang just invented the emails.
Non-repudiation is virtually always undesirable in general-purpose messaging systems. Revealing to a stranger whether a message is valid is a concession to that stranger, not a benefit to the email's owner. This property is called "deniability" and most secure messaging systems go way out of their way to have it.
It comes down to if a third party gets access to your emails (e.g. through a server compromise), should they be able to prove to a fourth party that the emails are legitimately yours, vs completely faked? Non repudiation through strong DKIM keys enables this.
Example: Third party is a ransomware gang who releases your emails because you didn't pay a ransom after your email server was compromised. Fourth party is a journalist who doesn't trust the ransomware gang, but also wants to publish juicy stories about your company if there is one, but doesn't want to risk their reputation / a defamation case if the ransomware gang just invented the emails.