Tolkien was a writer of fiction. His Elvish languages were fictional. They were a first a private invention as a hobby, and then developed, so far as they were developed, as background material for the fiction he wrote.
There is no way in which any fictional language can be
automatically updated
. Forms in any fictional language depend on whatever the author of the language invents and on whatever rules the inventor creates. Tolkien never set down anything like a complete grammar of either Quenya or Sindarin. And Tolkien might at any time change any of his rules, or invent a new rule.
In letter 347 in
Letters of J. R. R. Tolkien occurs:
The names in the line of Arthedain are peculiar in several ways; and several though S. in form, are not readily interpretable. But it would need more historical records and linguistic records of S. than exist (sc. than I have found time or need to invent!) to explain them.
The same is true for many other oddities of the Elvish languages.
Arvegil145 asks, “
meril (rose) is valid in Sindarin, but what would be the Quenya equivalent?”
I see no reason to believe that the Quenya cognate would not also be *
meril, but see no reason to think that such a Quenya form existed, or necessarily had the same meaning as its Sindarin cognate. Tolkien gives several cases where a supposed cognate form does not exist in the other Eldarin language or exists with a different meaning.
Arvegil145 asks, “But what about the hyphens before and after "i" in the name of Meril-i-Turinqi?”
Hyphens are elsewhere used by Tolkien to indicate that the hyphenated form is a single name in the form presented. The form
i is in later Quenya translated ‘the’ in the poem
Namárië in the phrase
i falmalinnar ‘the foaming waves-many-upon (
pl.)’ So
Meril-i-Turinqi might be literally translated as ‘Flowers, the Queen of’. Again, this is only a guess.
Read the essay
http://www.elvish.org/articles/EASIS.pdf for the disgust that such guesses have raised in one commentator on Tolkien’s Elvish.