Finally the real story thanks George Brown

Mine continues to defy the rules and thus far no TMCC operating problems anywhere, up or down.  However, we're adding a new 140 foot long upper section, and as it will be above ALL the other trackage, we're putting in the ground plane/antenna enhancer-extender magic wire along side all the upper trackage, and connecting it to the non-code way of a plug using only the ground prong as the "ground".

GHD posted:

Run 291 has the true story article that explains why I have so much ground wire run on my 3 level layout. It sure would have been nice to know and understand this years ago. Oh well. We figured out the hard way how to make this system work. Thanks George for the article.

Well, Dale Manquen published some very good information on TMCC signal propagation years ago: TMCC Signal Basics by Dale Manquen, so the information was available, apparently not as widely known.

Thanks John, I was not aware of this. If the date of 2011 for this article is correct, that's about 10 years after we started the learning curve. All is well now, and my layout is well grounded in case of a lightning strike. 

I suspect a lot of folks were not aware of it, although it's been mentioned here a few times.  Dale had a lot of background in the TMCC workings, bright fellow.

The antenna extension wire aspect, providing signal from the house wiring to the lower track locomotive, rather than "protecting" the upper track from signal overdrive makes sense now that it is not a way of grounding out an excess signal.

From Dale's treatment of the subject.

Avoid overwhelming the airborne signal with too much conducted Track signal

1. Do not connect tubular track ties directly to metal bridges with metal mounting screws. Alternatives are nylon screws or using insulating shims and plastic shoulder washers.
2. Beware of trackside accessories with metal parts that are tied to the layout’s common bus. This will put the conducted Track signal onto the metalwork. One solution is to use a separate transformer and wiring for accessories that are not tied to the track common.
3. If necessary, add some earth ground antennas in the region where there is too much conducted Track signal. Run a wire connected to earth ground on the underside of the bridge or between the parallel tracks, or string some fine wire as power lines on power poles.
4. We can temporarily augment the airborne signal by using our body as a secondary antenna, and placing our hand near the locomotive. This brings more earth ground signal to the locomotive. If this helps the locomotive, the permanent fix is to add an earth ground antenna to that area.

What a great explanation of Dale!  I suppose if you get all "techy" you could argue standing waves that reinforce and cancel that 455KHz signal between the U terminal and actual earth ground occurring over various green wire lengths.  But hey who cares as long as TMCC works.  Being exclusively in the DCS camp, I found the explanation very interesting and enlightening.