[nprateem]

If you decide you no longer want to receive email from [e-mail] it's easy to set up a blacklist filter. If they circumvent that and email you at [e-mail] you've lost that alias and easy way of blacklisting them. And presumably if someone had wanted to be contacted at [e-mail] they would have provided that email in the first place. So I don't think your analogy holds.

[oarsinsync]

Fair, the analogy doesn't hold onto the functions provided, but RFC 5233 is very clear that the user+detail separation does not provide any privacy protections, nor can it.

The 'user' part is still public information, as is what it's used for. There should be no expectation of privacy for information being used per specification design.

The usability trade-off is a shame, but the solution was half-baked at best, and is primarily useful when combined with privacy-sacrificing public email providers. When you have greater control of your email, distinct 'user' parts can be used, which does provide the privacy aspect desired.