philemot, I think you are on to something with the triangulation, but I don't believe that is the entirety of the issue. In the image I posted above, the cloth mesh is a Marvelous Designer 2 Delaunay Unstructured Tri-mesh. Absolutely no quads, or n-gons in that mesh, and it displays correctly in default VWD (Poser).

Reading your assessment of the issue made me remember testing in default VWD, and employing Gérald's subdivision triangulation algorithm on collision objects. I was getting the same artifacting, so it might be something in VWD that is causing it, and not the exporter. I don't remember getting any artifacting on any of the cloth meshes I utilized the Sub-D algorithm with, so I didn't report it as a bug. Now, I believe it is a bug that should probably be addressed.

I went and found some screen-shots I took when I was performing tessellation testing. Below are examples in default VWD that show base collision objects without artifacting, and then with artifacting when Sub-D algorithm is used.

Stairs collision prop default:

Stairs collision prop Sub-D on:

Sword stand collision prop default tessellation:

Sword stand collision prop Sub-D tessellation (normal and wireframe):