Indeed, normals are nice and crisp. By inverting the Y channel I can replicate the problem you had, so that was definetely the problem. The seam you are seeing now in the right of your image, it's 99% sure a diffuse problem, not a UV problem. Make sure you paint your UV's atleast 8-10 Pixels extra out of the actual UV…
Sorry, yes everything is very factually correct and well written (and should be pinned imo)! It's a great document to explain to people having trouble with their normal bakes. Basically down to, yes if you have time to do hard edges baking and setup, go for it! not all models require this though, and sometimes its…