Each email adhering to some rule (magicmarker[a-f0-9]+)goes to my account.
Each registration anywhere gets unique email address generated as magicmarker<b64(hash(domain+salt))>@mydomain.com Salt is there to keep it unguessable.
When I get any spam, I can redirect it to /dev/null and verify from where it came from to sent hate mail to domain owner or whatever.
0 spam. 0 tracability. Ability to track who sold/leaked my mail address.
The one I use (purelymail.com) allows for underscores to serve this purpose, which will never be stripped. It's also super cheap (less than $1/month), though because of its low volume and AWS IP, my messages have a problem with getting marked as spam. The next comparable service I found that offered effectively infinite addresses was $50/year, so I fall back to gmail if I really need to send email.
IME: I’ve never had anyone remove it (although some don’t accept it and others will have bugs that result in an unusable account if you register with it.) I used one with the company I most recently interviewed at (they used a third party service for the HR site and I’ve had trouble with sites like that selling my email address which is just so enraging honestly.) Every. Single. Time. I logged in to fill out a form after getting hired I had to call HR and have them reset my account because of some weird bug.
Though similarly, email usernames ('local part') are case sensitive but I've never encountered a mail server where this was the case. I imagine if a nefarious party stripped the markers, they'd lose the tiniest percentage of their audience that way.
(Aside: Your own approach to using + is quite clever as it's the total opposite to most users, so you'll see who pulls this trick ;-))
Several email providers treat a + symbol as the end of the first part of the address and ignore everything between it and the @.
I think the responder’s point was that analytics providers just ignore things after a + too