RFC 822 describes how messages are encoded when email servers talk to each other. It isn't really about email address validation and is not intended to be used to validate a form field on some registration page.
Unless you're writing an MTA or similar piece of infrastructure there is no reason you should be using the RFC grammar. Even if implementation were easy, it probably isn't what you want. For example, the spec permits inline comments but that's a nonsensical thing to have in the middle of an address you typed into an HTML form. Email addresses entered on a web form should be rejected if they contain comments, IMHO.
I think what most developers really want to know is something like: Can this given email address receive messages? Or: Does this given address actually belong to this user? Well, the only way to test that is to send it a message. At best, regex validation might warn you earlier that a given address couldn't possibly work because it's so obviously malformed. But you can't validate your way into getting people to enter their real email address if they don't want to or if they don't know what it is. If your intent is really just to help catch typos and mistakes, you'd be much better off looking to something like mailcheck [0] which will flag common typos like "foo@hotnail.com" even if they result in valid looking addresses.