I sometimes simply abandon a reply in mid-edit - pretty much a self reap before posting. Using the preview button and actually reading what you have written often aids in such a decision.
The most common source of duplicate posts I've noticed is when a node is posted by Anonymous Monk, then is duplicated by a registered monk. Perhaps a solution to that is to provide a way of changing ownership of the original node so it doesn't need to be duplicated? I guess this could lead to problems with people trying to claim nodes they didn't author so it's not clear that this solution would be better than the (relatively minor) current problem.
Perl is Huffman encoded by design.