After a brief scan of the topic and 2 mins of experiments, the 'issue' is clear...

The artifact you are seeing happens at "any uv-seam, around the cylinder".  The reason that flat-mapping eliminates the artifact is because flat-mapping produces no uv-seam (no 'splits' between the vertical side polys of the cylinder).

Forget everything else and all other speculation related to Normals (Poser ignores any normals in the .obj file anyway), ordering and split vertices etc.  This is a 'uv-seam' issue. One seam == one artifact.  If you have 4 seams (ie. a Box Mapping), you get 4 artifacts.  Zero seams (flat-mapping) == zero artifacts.

With that out of the way... I currently have no idea 'why' this is causing artifacts in Poser, but I'll give it some thought (I was on the way to hit the sack when I found this thread).

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