The Nandor dilemma as I see it, with respect to them being Eldar or not.
According to Appendix F, most of the Elves of Lorien and Mirkwood were East-elves, whose languages were not-Eldarin. And we can hardly say that JRRT forgot this section entirely for the revised edition, as he added a footnote to try to
re-characterize this very thing about the speech of
the Elves of Lorien specifically . . . that is, "now" these Elves speak an Eldarin tongue (Sindarin), but with an accent.
I'm not sure how well this holds up with what is said in the Lorien chapters though. Frodo was not the only one that could be misled by an accent.
"They had little speech with any of the Elven-folk; for few of these spoke any but their own silvan tongue." "Silvan tongue" aside, did their speech mislead Aragorn and Boromir too? And often "they" (the companions) heard nearby Elvish voices singing, but if Legolas was with the Company
"he would not interpret the songs for them"
Again, if these Elves were speaking Sindarin with an accent, is the suggestion, at least, that even Aragorn was not getting it? Or Boromir?
Possible.
Or are we now supposed to imagine that some in Lorien spoke a Silvan Tongue, others Sindarin with an accent?
Or . . . just call it Silvan Elvish
Anyway, in some posthumously published texts, and thus in the constructed Silmarillion, the Nandor are Eldarin, but this contradicts Appendix F (see below), and given CJRT's later entry in COH (at least one of the entries!) he seems to want to "return" to a definition more in line with what his father actually published. But instead of using that "five letter word" (canon), I'll put it this way, similar to what was done with the Lost Tales: in the tales Tolkien himself published it was easy:
Eldar = West Elves = Elves who passed Over Sea plus the Sindar only. And the languages of The East Elves (most of the Elven Folk of Mirkwood and Lorien) were not Eldarin -- makes sense, they weren't Eldar.
Less easy perhaps (second edition), as noted, JRRT adds that Sindarin
was spoken in Lorien at least, but with an accent:
"And this "accent" and his own limited acquaintance with Sindarin misled Frodo." Cough. Okay. But the idea still remains that these East-elves are not Eldar, even if they learned an Eldarin tongue.