I agree that we should not change the draft on the 3156 question.
Everything that needed to be said has been said, so I'll just comment
on this:
What happens if the "- " prefix causes the line to exceed SMTP line
length limits (998 characters)?
As I see it, nothing, any more than a too-long line would be when not
dash-escaped. Armor is not email (or any transport) specific. Just
like the very common line-wrapping problem, if there is a desire to
transport a message through a system that has line length limits, it
is incumbent on the sender to do it in such a way that the message
survives transport. We even mention this in the draft, albeit in the
context of Armor Headers.
David