I believe he was talking about having the vertex normals split where the UVs are already split, hence "harden edges of uv islands," which is of course free. Personally I split up my UVs from how I split my normals, because it gives me 80% of the unwrapping done at the click of a button.
Have you triangulated the mesh, or tried baking directly in xnormal the final tangent space map? if you have an object with a lot of soft edges...something like a rounded hull, and you can't harden them all, it is preferable to sync the baked map with the engine, you'll avoid any artifacts that may appear. For hard…