The use of a "+" convention is just a convention popularized by Gmail and the other major providers. If you have your own domain, you should be able to do this with any arbitrary text schema, and encode some information in the address itself, especially if you don't care about sending email from those aliases: set up your email service to have a catchall inbox that can further be filtered/forwarded based on other rules.

It can be cumbersome but I could see it working at getting the information you're looking for.

Ah, it's more about the receiver than the sender. If they cut it off, their letter gets deleted or moves to spam directory. Provided someone configures that.

With centralized mail services of today 1990s' techniques don't work so well, but that's a problem of adoption, not allowing mail without a correct token is still pretty modern.