I haven't read this whole thread, don't really want to now that it's 6 pages long, I've only read this page, I'll just chime in to add that:
1. Zero frets suck, I hate them, they look stupid, they're a pain in the ass to deal with when they wear, and they're much more difficult to properly replace than a properly cut nut.
2. Zero frets will do nothing close to what a compensated nut will. They will never act as a compensated nut period. Whether it's a standard nut, or a zero fret, they both accomplish the identical thing. The only fret that becomes critical with a nut or zero fret, is the 1st fret. If your nut action is to high it affects overall action, but if it's to low, it ONLY affects the open note, after the 1st fret is fretted, your nut or zero fret is irrelevant when it comes to fret buzz.
So, what does the nut or zero fret accomplish, it will affect how much the string goes sharp when you fret a note. The lower the nut action, the less the string goes sharp, the higher, the more sharp it will play.
Now, a compensated nut adjusts the scale length somewhat, think of it as intonation. Remember, your adjustment at the bridge will ONLY affect fretted notes. The string behind your finger no longer comes into play when you talk intonation at the bridge.
The compensated nut is basically intonation at the nut, like your bridge, only now, it is affecting the open note since you are actually changing the scale length of the open string. By having less tension on the string (short scale length) you reduce the amount of tension placed on the string when you push it down. OF course each string and each scale length has a different tension, so the compensated nut adjusts for the amount of tension change when the string is fretted, equallizing it somewhat. This is what gives you better intonation with a compensated nut. It has changed the tension of the string overall. This allows the guitar to be in closer fretted tune with itself than harmonic tune. (ever notice how a guitar where the intonation isn't set can be perfectly in tune with 5th and 7th fret harmonics, but when you fret the 5th to open it's way off?)
Anyway, this is wordy and confusing, I didn't understand how most of it worked until I took the Buzz Feiten course, but it does work, I find that the average person will never notice the difference even if they think they have great pitch, but you notice a huge difference on the strobe tuner.
So, in conclusion, properly cut nut, and zero fret, identical idea.
Compensated nut, something completely different.
So, this comment
Is completely false, a zero fret will never accomplish the same goal as a compensated nut.