sure, in the led 1536, but the older panels we're talking about were multiplexed, so the data would only have to go through the (shift registers for the) previous leds on the same row

you obviously know a lot more than i do, so maybe i'm missing something, but in either case i wouldn't expect noise or reflections, the signal levels and timing get restored at every shift stage, even low voltage cmos usually has more than a volt of noise margin, the traces are pretty short, and we're talking about longwave to shortwave frequencies, not microwave frequencies