Gmail, and some other systems, support a very old email standard that needs a name. Gmail will treat email@example.com as though it were firstname.lastname@example.org. It’s handy for filtering email lists.
I wondered if it could use it with Facebook accounts. As I discuss in my book there are many reasons to have Facebook related email for a vulnerable user go to their parent or “Guide”. Facebook doesn’t allow an email address to be associated with more than one account — maybe the + feature would work …
Except it doesn’t. I tried adding a + variant of my personal email to one of the kids accounts and Facebook told me it was in use.
Bummer. Now you know not to try.
Incidentally, iCloud support up to 3 aliases, so you can do this with an iCloud email alias. Alas, regular Gmail does not support true aliases — only the + suffix trick. Google Apps does support aliases, at least if you own a domain, but that’s strictly a geek or business thing.