You made the statement that any modern Nikon lens has weak edges on FX. I think that is mistaken. Any, I think this issue is best left before I lose the will to live. Though I am not sure these posts constitute a definition of life.
A word of advice. If you want to leave an issue alone, then don't continue to yap at someone's heels after he has corrected his mistake, and even worse, misrepresent what he actually said as a final nip.
This is what I said: "This seems to be a common problem with any modern Nikkor lens, weak in the corners on FX....."
Now I've already agreed that the above phrase is poorly worded and misleading and you were quite right to bring it to my attention. I should have written something like, "This seems to be a common problem with lenses designed for full frame 35mm, weak in the corners" without creating the impression that Nikon lenses might be worse than other brands in this respect.
You then continued to badger me to provide evidence, asking: "Where is your evidence that any Nikon lens suffers from 'weak' corners on FX?"
I provided that evidence. The Nikkor 50/1.8 would appear to be particularly poor in the corners on an FX camera, certainly poorer than the Canon equivalent, which is not to say with more research one would not find a Canon lens which is significantly worse in the corners than the equivalent Nikkor lens.
The awareness I've been trying to create in this discussion is that corner softness of lenses when used on full frame cameras is a common problem. Even on cropped format cameras, corner softness can sometimes be an issue, which is why Photozone charts always include the performance of a lens at the 'border', not in the extreme corners specifically, which would result in an even worse figure, but in the borders which include the short edges of the format.
It doesn't take much imagination to deduce if a lens has noticeable softening at the edges on the APS-C format, it will be much more noticeable on full frame.