The reason I found this thread is because I bought this TV a few days ago, and at some point on my Xbox One opened up Internet Explorer/Microsoft Edge. When scrolling up and down on the xbox.com website (I think), it was text and images against a white screen. That was the first time I had ever seen ghosting/smearing in my life, but I instantly recognized what it was. I was concerned I might get ghosting while playing games, but I booted up a variety of Xbox One games (Skyrim, Rainbow Six Siege, Banjo Kazooie on Xbox Arcade, Titanfall)...I didn't see any ghosting or smearing. Or at least I didn't notice it. I also felt like the response times were great and very playable. Granted, those games did not have instances of dark objects appearing on a very white background, so I couldn't tell.
I also watched a bunch of Netflix, YouTube, and 1080p cable TV, and did not notice any smearing. However, the nature of the content was such that it probably didn't have many (or any) instances where one would notice, i.e. dark images over a light or white background.
After seeing this thread, I went ahead and viewed some of the videos you all shared:
1) Verizon | Jamie Foxx - "Limited" on YouTube. I could see a bit of ghosting at the end where, if the black suit quickly disappeared from the screen, some black color would be left on the screen for a fraction of a second. I also could see some text ghosting away towards the end of the video.
2) Moving Dot Motion Blur Test on YouTube. I got similar results to what someone else posted. I went to Advanced Settings->Motion and turned MotionFlow to Standard and CineMotion to Low, but I didn't notice a difference in smearing effect. I normally prefer MotionFlow to OFF, because I prefer the way TV and movies look with it off (as they were seemingly intended, rather than ultra smooth which in my opinion makes it look like a home video).
3) I watched the Bananya - Ep 1 video on YouTube. I did indeed notice one or two brief moments of smearing when the video switched from the banana to the cat and then bubbles or something appeared. Oddly enough, after watching it a 2nd and third time, I no longer saw the effect. Maybe I became immune to it? I just couldn't notice it as much at all.
Time will tell how annoying this feature is...so far I haven't noticed it during actual normal use (except for the internet explorer on xbox one). Not sure I'd notice it even if I went looking for in normal use....