Wear marks on chains I am generally using SRAM chains with a powerlink. For a new chain there is no indication of a preferred pulling direction or inside/outside.
If we demount a used chain that has never been taken off before at, say, about halfway life, are there obvious wear marks that show in which direction it was pulled and which side was on the outside?

Does it make sense to maintain the direction and orientation, or perhaps to reverse one or the other?
It makes no real difference - the rollers in a chain turn all the way around, and the wearing surface is the internal diameter of the roller, not the external diameter of the pin.

There are some fancy chains which have a marked outside and an inside, and may state a top and bottom too, but this is more about matching the shifting lands and pins and ramps on a cassette.

Some chains are asymmetric in their outer plates, which looks "wrong" if installed upside down.

Other chains, noticeably half-link or BMX chains can have plates over the top, so the two outer plates are one piece folded over.  This is done for strength, and cannot be flipped either.   These chains don't work with derailleurs so you're unlikely to have one.

 A chain that can be reversed but not flipped.