With most decoders the settings of accel and decel in CVs 3 & 4 will moderate the transition from fwd to rev in the 28 speed step mode. However, the transition can be rather jerky if CVs 3 & 4 are set to zero. Not very prototypical operation and as you point out, possibly detrimental to the life of the decoder, motor and gears. There were a few early decoder models that treated the 128 speed step mode differently than the 28 step mode in this regard. Those did cause an abrupt change in direction and a big step in motor current if you pressed the direction button on the fly.
---In WiringForDCC@..., <brian@...> wrote :
I was watching someone engaged in low speed shunting recently. He
was using a NCE PowerPro and instead of bringing the loco to a
halt and reversing the direction of travel, he was just pressing
the Direction button.
Regards and thanks