You seem to have difficulty following the logical throughline here. There is no playing dumb in the previous comment. Let's put it in a statement instead of t

You seem to have difficulty following the logical throughline here. There is no playing dumb in the previous comment. Let's put it in a statement instead of the form of a question: it does not follow to respond to the quoted part ("URLs aren't an authentication (or authorization) system") with remarks about "those of us living in the real world where billions of people access millions of systems via websites using their email address as ID/fallback[...]". You (both of you) are confusing the subject here: URLs vs reaching back to drag emails and their privacy into focus. They're different fucking things! Stop responding to comments about one with responses that deal in the other! Billions of people access websites using their email addresses? Granted! Now say something about URLs if that's what your quibble is and shut up about the emails that the URLs were sent in and whether or not those emails are private. The comments about email are misdirection at worst, and a sign of unclear thinking (and a hazard to confuse others) at best.