Thanks, a phone call will probably clear a lot of my confusion and issues. I will call in the next day or two. I re-read several forum posts going back a few years on this very common and recurring issue. Carl Siebert's explanation that these all just end up in a "bucket" of individual searchable keywords is enlightening for sure. I think I am largely distracted by the "ugliness" of the displayed keywords in the Catalog - Browse - Metadata - Keywords view. I would leave it at that, but the "ugliness" carries over into other apps, notably DXO Photolab, which has also been discussed on this forum.
So this obnoxious Lightroom duplication of fields in the XMP is clearly NOT the fault of Photo Mechanic, and even if Camerbits decided to "hide" the duplicates, they would still show up in some other software. What I would REALLY like would be some way to strip that LR field showing "flat" keywords, so that PM, DxO, and other software would have one set of keywords (Structured) to work with. Does Photo Mechanic have this (stripping) capability, or does anyone on the forum know of software that does? I have NONE of this issue with files tagged AFTER leaving LR.
Thanks....gary