At one point, we had a system which performed best when is 100/MB half duplex mode. (purely anecdotal evidence). It was plugged into a switch with other systems running at 100 Mbs full. Seemed ok and NW guys did not report any issues.
But how can you have systems on the same switch running different duplexes like that? Won't the 100Mbs half systems basically try to use CSMA/CD and 'disrupt' the other attached systems? I did not get a very good answer from the NW person at them time.