I hope to dear Lord that this is a redundant overused, but paltry quip of some sort. Nagato, a better sensor than Karin? You mean a Senor who can even tell that so and so Chakra belongs to a freaking Dog from such a large distance away is a worse sensor than Nagato? My goodness. So in your attempts to prove me wrong, you are basically out of argumentation that now Karin has been given a lower sensor status?
Just admit it that you are wrong, because this is not even a sound argument.
Hollow and an explicitly weak argumentation. Keep reusing it over and over again. Nagato even mentions that it's not Amaterasu. Now it could be implied that Itachi withheld it, but, we cannot say that for sure.
Karin didn't sense it either, and she's the best sensor in the entire manga, sorry to burst your bubble. You know, sift through your insults and most of them make you look like a bitter 12 year old, crying over his first zit, no offense. At least be civil when you discuss something. I for one, cannot take you seriously on these grounds alone.