I read Bill Calfee's article from another thread and began to think about those vibrating guitar strings and what it took to "play" a harmonic. It became obvious that rather than a "X" crossing of the vibration pattern it must have a "flat" in the pattern...not "parallel" but I used that term as a tie to previous thoughts and as an acknowledgement of the concept.
As for those "second thoughts" mentioned, I suffer from such on a continuous basis. The article I read was an indication of the "real" Bill Calfee...not the one that posts here.
Back to the "obvious" flat in the vibration pattern. A guitar string touched at any point other than a harmonic will be "killed" instantly. A casual touch, as opposed to an exact touch, at the harmonic and the string still plays. Since you can do that with a fingertip, a logical assumption could be drawn that there is a width or range involved....not swingin up, down or otherwise. A very narrow range when compared to the barrel length but a range nonetheless. Were it an "X" pattern, you would need something like a knife blade to play the harmonic.
Edit:
"when compared to the barrel length" should read "....string length"