Comments in parentheses are a feature of MIME, and have nothing to do with delivery of e-mail: those comments are not valid in the envelope header as parsed by SMTP. (Put another way, there is no "the RFC": there are multiple RFCs used for different purposes and which have different rules.) MIME certainly has no relevance to your address book, and if your structured address book database is attempting to parse an e-mail address as if it were inside of either a MIME header or an SMTP envelope, you should absolutely complain: that should be considered a bug :/.

Think about this: one would hope that if you use characters in that field which would normally need to be escaped if used in a MIME message, and that e-mail address were to end up in a MIME message, that the e-mail client would get the unescaped e-mail address from the database and would then escape it correctly--and by "correctly", we mean a different way of escaping it for MIME vs. escaping it for SMTP--the same as we would expect its usage in an HTML page, an argument to a shell script, or a value in an SQL statement, to also be escaped for each specific purpose.

Huh, TIL. I've never actually used comments in an email address, as they're pretty damn silly. I must have misunderstood the stackoverflow post I read way back.

Thanks for the information!

Email address comment? What the hell were they thinking?

Think about pre-outlook days, you may want some notes to remember who you are emailing.

I'm thinking about it. Still doesn't make sense to put it in the address.

Like plus aliases (chad+foo@), Dialer can find chad()@. However the parentheses cause at least 2 minor annoyances (desktop Gmail doesn't let me email such an address, and the Android contact editor won't let me edit the contact.)