After a year long deprecation period, I have switched off the email address firstname.lastname@example.org where originally you would forward your receipt emails.
I liked the user-facing simplicity of a single address along with the "magic" of figuring out whose each email was. But to avoid false positives (one user seeing another's email) the code had to be very conservative, which led to a few false negatives (email not getting linked to its owner at all).
Starting a year ago everyone has had their own unique forwarding address. This substantially simplifies the code, avoids any false positives or negatives, and is no less simple for the user.
It's nice to tick this off after waiting for a year!