Please see this card, which has just been moved back to the Trello development board.
Card order within a list is meaningful. When you change the order of
cards in a list, it means something and is reported in a notification.
This presents special challenges for the design of any sorting
functionality we might consider.
When you sort, who sees it? You or everyone? Is it reported to
everyone? What if you inadvertently sort and destroy a list order that
was meaningful? Do we need to offer recovery/undo options?
If sorting is just for finding cards, do we offer the ability to sort
only for your current view of the interface? How do we reflect that to
you so that you don't think you've re-sorted for everyone? What
happens if someone changes the order of a list while you have it
We would need to support sorting temporarily, for viewing, in which
case you wouldn't be able to reorder the cards, and everyone else
would see the current order, and "solidifying" that sort, which would
be reported ("Rich Armstrong reordered the Ideas list by Votes.")
There's clear value in being able to find things in lists, but sorting
can be really problematic.
For the foreseeable future, we're likely to focus on improving
filtering before tackling any sorting.