Hey, let's remain on the sane side of the Force. If voltages below 20 result in problems while unlocking, I just imagine what may happen during more demanding (instant big differences in current) situations.

I'm also not 100% sure about risk of filesystem corruption because of "sneaky" undervoltage (one that doesn't result in reboots, but may result in CPU calculating with errors), but I do believe, that I encountered it once, long time ago. Despite being careful with things I install, many things started to act bizarrely, or just get plain broken, and it was getting worse over time. I was using so-called "ideal" undervolting profiles - without random reboots - and it was one and only time, when I had to reflash - after that, installing the same packages etc, but using custom profile with much higher voltages, I *never* encountered such problems again.

So, as I've said - I can't be 100% sure, but it seems to me that it isn't urban legend. Saving battery life is cool, but lets don't get over-excited with it, and remain in sane, 150% stable values, +1 value up, just in case

/Estel