In article <CAF1dMVE_-YME=0QKormaY8QUkr5ebm+zOJbDKOM6DxGFkyvMFQ@mail.gmail.com> you write:
>- There are several places where 'folder' and 'mailbox' seems used
>interchangeably in the doc and could lead to confusion.  Need to pay more
>attention on subsequent edits.

A mailbox can have multiple folders.  I'll see if I can make that clearer.

>- The doc stated that using A-label in mailto: will shorten the whole
>string, which sounds like an encouragement.  I'm concern on that.

I don't feel strongly about it.  I would expect addresses to work
whether the domain is encoded as U-label or A-label

>- I would love to see more write up regarding spam filtering, particular on
>determining whether certain character is valid or not (even calling it out
>of scope for this doc), and to raise awareness that detection algorithm may
>detect downgraded message as suspicious/malformed/etc.

It shouldn't.  Remember that UTF-8 is already valid throughout message
bodies, and propertly downgraded headers are all ASCII.

R's,
John