Hi,
By way of coincidence I was just looking at a post in the barn that is needing a new section spliced in and it has scoring marks facing down though I cannot say if this is representative of any standard practice. I don't think so though because there will most likely always be scoring markes in opposite directions unless, as sometimes is the case hewing was done by right and left handed hewers or someone with extraordinary ambidextrous skills.

Greetings,

Don Wagstaff