[gandalf85]

To those comments I don't respond to, I agree.

LO-18: OK, I get it now.

LO-40: I think "children of Finarfin" is probably the safest choice. Although I do like the sound of "Finarfinians".

LO-54: Then I think the only explanation must be that not all Men abandoned the language. The addition of "many" makes this more clear.

I added in parts Appendix F; almost all of the changes are references to events/people/places in the Third Age. There is lots of good stuff, it would seem a shame if we didn't use it anywhere. The section in Appendix F on Elves is a summary of what is included here, and the section on the Dwarves explicitly talks about their relationship with Men in the Third Age (or is a repeat of what is already included here). I propose adding this to the end of what you already have:

< LO-55 Appendix F The Westron was a Mannish speech...against the Dark Power of the North.
After the overthrow of the Dark Power...the Kings of Men, whom the Elves called the Dúnedain.
The Dúnedain alone of all races of Men knew and spoke an Elvish tongue; for their forefathers had learned the Sindarin tongue, and this they handed on to their children as a matter of lore, changing little with the passing of the years. And their men of wisdom learned also the High-elven Quenya and esteemed it above all other tongues, and in it they made names for many places of fame and reverence, and for many men of royalty and great renown. [Footnote: Quenya, for example, are the names Númenor (or in full Númenóre), and Elendil, Isildur, and Anárion LO-56 .{, and all the royal names of Gondor, including Elessar ‘Elfstone’. Most of the names of the other men and women of the Dúnedain, such as Aragorn, Denethor, Gilraen are of Sindarin form, being often the names of Elves or Men remembered in the songs and histories of the First Age (as Beren, Húrin). Some few are of mixed forms, as Boromir.}]
But the native speech of the Númenóreans remained for the most part...spread thence along the coasts among all that had dealings with Westernesse.
After the Downfall of Númenor, ...In the days of the Númenórean kings this ennobled Westron speech spread far and wide, even among their enemies; and it became used more and more by the Dúnedain themselves LO-57{, so that at the time of the War of the Ring the elven-tongue was known to only a small part of the peoples of Gondor, and spoken daily by fewer. These dwelt mostly in Minas Tirith and the townlands adjacent, and in the land of the tributary princes of Dol Amroth.} Yet the names of nearly all places and persons in the realm of Gondor were of Elvish form and meaning. A few were of forgotten origin, and descended doubtless from the days before the ships of the Númenóreans sailed the Sea; among these were Umbar, Arnach and Erech; and the mountain-names Eilenach and Rimmon. Forlong was also a name of the same sort.
Most of the Men of the northern regions of the West-lands were descended from the Edain of the First Age, or from their close kin. Their languages were, therefore, related to the Adûnaic, and some still preserved a likeness to the Common Speech. Of this kind were the peoples of the upper vales of Anduin: the Beornings, and the Woodmen of Western Mirkwood; and further north and east the Men of the Long Lake and of Dale. LO-58 {From the lands between the Gladden and the Carrock came the folk that were known in Gondor as the Rohirrim, Masters of Horses. They still spoke their ancestral tongue, and gave new names in it to nearly all the places in their new country; and they called themselves the Eorlings, or the Men of the Riddermark. But the lords of that people used the Common Speech freely, and spoke it nobly after the manner of their allies in Gondor; for in Gondor whence it came the Westron kept still a more gracious and antique style. }
Wholly alien was the speech of the Wild Men of Drúadan Forest. Alien, too, or only remotely akin, was the language of the Dunlendings. These were a remnant of the peoples that had dwelt in the vales of the White Mountains in ages past. LO-59 {The Dead Men of Dunharrow were of their kin.} But in the Dark Years others had removed to the southern dales of the Misty Mountains; and thence some had passed into the empty lands as far north as the Barrow-downs. From them came the Men of Bree; but long before these had become subjects of the North Kingdom of Arnor and had taken up the Westron tongue. Only in Dunland did Men of this race hold to their old speech and manners: a secret folk, unfriendly to the Dúnedain LO-60 .{, hating the Rohirrim.}
LO-61 {Of their language nothing appears in this book, save the name Forgoil which they gave to the Rohirrim (meaning Strawheads, it is said). Dunland and Dunlending are the names that the Rohirrim gave to them, because they were swarthy and dark-haired; there is thus no connexion between the word dunn in these names and the Grey-elven word Dûn ‘west’.}

LO-62 {The most ancient people surviving in the Third Age were the Onodrim or Enyd. Ent was the form of their name in the language of Rohan. They}Ents were known to the Eldar in ancient days...but they had no need to keep it secret, for no others could learn it.
Ents were, however, themselves skilled in tongues, learning them swiftly and never forgetting them. But they preferred the languages of the Eldar, and loved best the ancient High-elven tongue. LO-63 {The strange words and names that the Hobbits record as used by Treebeard and other Ents are thus Elvish, or fragments of Elf-speech strung together in Ent-fashion. 1 Some are Quenya: as Taurelilómëa-tumbalemorna Tumbaletaurëa Lómëanor, which may be rendered ‘Forestmanyshadowed-deepvalleyblack Deepvalleyforested Gloomyland’, and by which Treebeard meant, more or less: ‘there is a black shadow in the deep dales of the forest’. Some are Sindarin: as Fangorn ‘beard-(of)-tree’, or Fimbrethil ‘slender-beech’. }

Orc is the form of the name that other races had for this foul people LO-64 .{as it was in the language of Rohan.} In Sindarin it was orch. LO-65 {Related, no doubt, was the word uruk of the Black Speech, though this was applied as a rule only to the great soldier-orcs that at this time issued from Mordor and Isengard. The lesser kinds were called, especially by the Urukhai, snaga ‘slave’. }
The Orcs were first bred by the Dark Power of the North in the Elder Days...so that their Orkish speech was of little use to them in intercourse between different tribes.
LO-66 {So it was that in the Third Age Orcs used for communication between breed and breed the Westron tongue; and many indeed of the older tribes, such as those that still lingered in the North and in the Misty Mountains, had long used the Westron as their native language, though in such a fashion as to make it hardly less unlovely than Orkish. In this jargon tark, ‘man of Gondor’, was a debased form of tarkil, a Quenya word used in Westron for one of Númenórean descent; see p. 1185. }
It is said that the Black Speech was devised by Sauron in the Dark Years, and that he had desired to make it the language of all those that served him, but he failed in that purpose. From the Black Speech, however, were derived many of the words that were in LO-67 {the Third Age}later days wide-spread among the Orcs, such as ghâsh ‘fire’, but after the first overthrow of Sauron this language in its ancient form was forgotten by all but the Nazgûl. When Sauron arose again, it became once more the language of Barad-dûr and of the captains of Mordor. LO-68 {The inscription on the Ring was in the ancient Black Speech, while the curse of the Mordor orc on p. 579 was in the more debased form used by the soldiers of the Dark Tower, of whom Grishnákh was the captain. Sharkû in that tongue means old man.}

LO-69 {Troll has been used to translate the Sindarin Torog.} In their beginning far back in the twilight of the Elder Days, {these}trolls were creatures of dull and lumpish nature and had no more language than beasts. But Sauron had made use of them, teaching them what little they could learn and increasing their wits with wickedness. Trolls therefore took such language as they could master from the Orcs; and in the Westlands the Stone-trolls spoke a debased form of the Common Speech.
LO-70 {But at the end of the Third Age a troll-race not before seen appeared in southern Mirkwood and in the mountain borders of Mordor. Olog-hai they were called in the Black Speech. That Sauron bred them none doubted, though from what stock was not known. Some held that they were not Trolls but giant Orcs; but the Olog-hai were in fashion of body and mind quite unlike even the largest of Orc-kind, whom they far surpassed in size and power. Trolls they were, but filled with the evil will of their master: a fell race, strong, agile, fierce and cunning, but harder than stone. Unlike the older race of the Twilight they could endure the Sun, so long as the will of Sauron held sway over them. They spoke little, and the only tongue that they knew was the Black Speech of Barad-dûr.}

LO-56: These names wouldn't be known in the Second Age.

LO-57: Reference to the War of the Ring

LO-58: The Rohirrim don't appear in the histories until the Third Age.

LO-59: The Dead Men of Dunharrow refers to a people of the Third Age.

LO-60-62, 64: References to the Rohirrim.

LO-63: Explanation of words used in LotR

LO-65: Uruk-hai don't appear until the Third Age.

LO-66-68,70: Third age stuff

LO-69: Explanation of the usage of the word "Troll"

It seems that the decision to make this work The Lammas is somewhat restricting since we can't include anything about the Third Age. Could we say in LH-01 that this is "based on" or "derived from" the in-universe 'Account of Tongues'?