the only way to reorder these in git is with rebase, but that is flagged as a dangerous tool, and with good reason.
if darcs can find a way to do this it would really be worth switching to, but if not then it would fall short in it's claim of safely being able to reorder patches. doing so behind the scene automatically would really worry me about code integrity.
It is quite common to have people come to #darcs asking how to reorder patches. The answer to that is "why would you want to do that?" To darcs, the order in which the patches are stored in the repository is a transparent implementation detail, and there's no command to change that. Darcs users are not constantly reordering patches, they're just enjoying a bit more freedom on pull. In general, if you don't use commands marked as unsafe such as unpull, each repository is honest about the order in which it pulled patches: darcs will simulate patch reordering to compute merge results, but won't change the order of patches in the repository.
There's one "patch theoretical" thing which git does better than darcs (and a lot of practical things), which is that it tracks more explicitely which stuff was pulled from where when. That information is neglected by darcs, which cares more about when stuff was originally written, and it should be tracked somewhere. Still, this seems easier to add to darcs than adding darcs' freedom of workflow to git, for which, as far as I can tell, you'd have to embrace the patch-centric view of darcs.