Update: after about an hour the streaks are gone, whew! But before that, I called Apple Care, told them exactly what I had done, damp microfiber cloth, etc., and the first thing they said was: no water!
So I told him that the documentation said "damp" and that's exactly what I did. The cloth had absolutely no water dripping, so water couldn't possibly have leaked into the cracks at the edge of the screen, and also the streaks were horizontal all the way across the screen, which doesn't suggest leakage inside the screen.
He didn't know what to tell me, and just advised me to take the computer to the Apple store to have them check it out. A while later, the streaking cleared up on its own.
So I'm relieved about that, but this begs the question: what went wrong with this seemingly benign method - damp microfiber cloth - especially since I followed Apple's instructions to the letter? And then, how
should I be cleaning my screen? Really seems that this should be a no-brainer compared to more complex issues!
Thanks for any insight 🙂
Karen