Originally Posted by
wschruba
The chains are absolutely still directional (asymmetric, as Shimano says). The engraved plates must face out, or the shifting of the system will suffer. Not all of their chains are directional--just some of the 10/11 speed models.
Basically, the RH plates are shaped to better grab the chainrings, while the LH plates better interface with the cassette.
Huge functional difference versus, say, a generic KMC? No, not really...but why pay for Dura Ace and get performance several tiers lower with the wrong chain?
Upside down or rightside up.. the engraving can face out, but the chain will have a different leading edge for each of these possibilities. I thought I read it's more important due to the shaping/material of the inside plates, and not the direction per se.