Sometimes it would make sense to use plugs that cannot be inserted the wrong way - or at least make it _very_ obvious which way is the correct way. :p
Sometimes it would make sense that people read the manual before doing such a thing - or at least take a short look into the schematic drawing showing the correct cabling.
USB cables for DENEB must use what's available on the mass market to get them at decent prices (and allow people to connect internal drive bays, hubs, card readers). So going for a custom made (non reversable) connector would make the card more expensive, getting spare parts more complex and forbid connecting standard internal USB hardware.
So - not a good solution.
BTW, the SUBWAY/HIGHWAY/ALGOR uses the same connector, and we never had wrong attached cables there - so I thought this concept would also work on DENEB, but for some reasons this seems not to be the case (while the number of such incidents is still small compared to the number of DENEBs out there).
Michael