> Same here with various software (Blender, Modo, Vue...). Seems to
> be a problem of unmerged vertices (that share the same coordinates)
> as a "remove doubles" or "merge vertices" operation fixes this.

Yeah, points along a seam are not shared. This will cause some programs to display a crease there if they calculate new smoothing information manually. But if they use the smoothing information ("vertex normals") that is actually stored in the .obj file you wouldn't see the seam there.

I don't automatically merge the vertices there right now because that would mess up the uv texture mapping information which is also included in the .obj file as well...

I suppose that I could add automatic merging in as an option. Maybe it should be on by default if more people are expecting to have merged vertices than expect to have distinct uv texture coordinates along the seam.

- Michael