I can quite easily produce the purple smearing but not on the S-note intro video!
Maybe your not going crazy.😜
On a side note😊, I've had a Note 2 in my possession and apart from some lines, which can only be seen on certain grey backgrounds, it doesn't suffer the purple smear problem(Exynos one I tried didn't). If this issue continues to drive you up the wall, and considering all N900s you've tried exhibit the same issue, maybe consider a Note 2 (DittoNote3 ROM👍 or import a N9005.
Alternatively, rally together all the disgruntled N900 owners and sue the pants of Samsung.😂
Best of Luck either way.
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