Addressing a couple of points, it's been stated on that link and on other sites that this method doesn't trip Knox, and I've seen at least two other photos that shows this. It's certainly variant dependent. It could very well be ROM dependent as well in terms of AOSP vs TouchWiz based. As you can see, the Samsung binary is still present. I haven't checked out whether it matters because I've stuck with TW (I like being able to keep the stylus functional). If I ever decide to experiment, I'll find out if AOSP ROMs break Knox and, if they do, I'll decide then.
As for returning to service, there's no problem unrooting and returning to stock.
Yes, I'm on Jelly Bean. In fact, I'm on the Beans ROM right now. I haven't sideloaded Kit Kat. In fact, until I'm sure that FoxFi is functional in Kit Kat (that's very much an open question at this point), I won't be upgrading.
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