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As said in the thread you linked to, add the albumartists tag.  If you use Musicbrainz Picard to tag your files with then all the other tags should automatically be set correctly for Kodi provided you pick the correct release in Picard.

The exact tag name varies depending on the tag system you are using.  Vorbis tags have different names to ID3v2.3 and some of those differ from ID3v2.4.
If you want a good experience from your music library then setting the Musicbrainz artist and album ID's is more than just useful   Kodi understands those tags and uses them internally.

Setting a compilation tag will tell Kodi that the album is a compilation but that is not the only way that Kodi can identify a compilation album when it scans your files.

My best advice is to get yourself a copy of Picard and tag all your stuff with that (having modified the script settings as detailed in the thread you linked).  Although it will do a pretty good job of matching stuff up, there will no doubt be occasions where you will have to visit the site to manually match up your albums using the 'tagger' link.  I'd suggest putting a bunch of albums into a new directory and use those to learn the workflow before you 'do it for real'.  You can add that directory as a source in Kodi and scan it in to see how the results compare to what you have now and then remove that source and the associated data when you start on your library proper.

Mainly I have found that Picard does a pretty good job for most of my albums but there are occasions when the length of my ripped tracks doesn't quite match the data in MB and I have to manually drag them into the right place or it has identified tracks as being from 3 different albums when they are actually all from one.  This also needs correcting manually by dragging and dropping the tracks into the correct place but the workflow is quite simple once you get used to it.

Thanks for clarifying. I have Picard but my library is far too large to be tagging/retagging with a GUI tool. To wit I use mutagen scripts which also generalises tags across formats.

I'd still love that list clarified a tad and find that it's all a little confusing.

I read that thread but feel a tad vague all the same. It suggest setting this in Picard: $setmulti(albumartists,%_albumartists%)

And so I'm left wondering:

1. What is the COMPILATION tag's value? Where is it documented. I found a hint that it should be set to 1 to flag that an album is a compilation.
   
2. I guess I can find the names of the MusicBrainz album and artist ID tags with a Picard experiment. I use MusicIP myself which is what MusicBrainz spun off from if I recall but is long dead and I rely on old 32 bit binaries to produce kick ass Music IP mixes.
   
3. The difference  between "Album Artists" and "Album Artist" remains unclear. The latter clearly should read "Various Artists" on a compilation, the former, in plural, wants what? Does it want a list of all the artists that contributed (in short the concatenated list of Artist tags form the the individual songs in the album?)
   

It would be nice to understand how to tidy the Albums view, and not see all the individual songs from my compilation is listed there. The compilations view is good but also unsupported in Kore and Chorus2  at present.