However: it seems that when you're offline (eg: away from wifi / on a plane, etc) the app becomes Read Only. This means no adding to cards, creating new cards, etc.
Is there a technical limitation which means that changes made offline couldn't just be sync'ed back later on?
(I don't speak for the Trello team, but I remember trying to reason out whether we could do something similar on FogBugz, and rapidly concluding that the real answer was "absolutely not.")
You're absolutely correct though - yes - this quickly becomes a way bigger issue than I originally gave it credit for in my HN-esque knee-jerk comment. I'd still love to be able to leave comments on a card though.