I would not be surprised if the "unmeasurable" artifact irritating to Dpe's and other's ears is related to the torsional distortion related to a ribbon's twisting (slight as it may be). Planar's do not suffer (or suffer less) from this problem, due to the increased stability provided by the planar's substrate (typically mylar), albeit a planar speaker may not be perceived to sound as "fast" as a ribbon.
Over the last thirty-five years, I have yet to hear a ribbon (not to say this may not happen) without a "sheen" to its character. Some people like this, some don't. I find the sound of ribbons to be interesting, albeit one, over time, to be fatiguing, and at the end of the day less like music, instead, more effect driven.
Their simplicity offers a very high cool factor: secure a thin strip or strips of aluminum within a strong magnetic field and transform ac voltage from the amplifier to modulate current to the ribbon. What could be simpler--taking into account simple does not always mean easy?
There are still some aspects of audio reproduction that have yet to be measured. And even if we arrive at a point where we "believe" all that can measured has been taken into account, at that same point in time we will have lost our senses.
My suggestion: don't lose your senses (as whimsical and unreliable they may be for discerning an enduring, unchanging "truth').
If a given sound brings up a red flag, per se, it is worth trying to understand the source of the red flag (it may be the polarity of an AC plug needs to be reversed?).
In today's world of "measured perfection," many have become less and less attuned and trusting of their senses and gut feelings, change as they may over time (welcome to maturation). Measurements may provide an interesting map to look at, but the territory is for each of us to discover on our own.
