[epistasis]

> Spammers won't respect the + either, they will clean their list of any +tags before sending.

That's the entire point, if you get an email from the site but it doesn't include your +servicename tag then you immediately can immediately tell it's a phishing attempt or spam. If the tag is there it's not a 100% guarantee that it's legit, but absence of the tag is a big red flag.

[pests]

You can't tell who it came from though, unlike my method at least.

Also, the +tag could get lost though just normal data clean up / normalization.