Oh, this hits hard. The idea that there were elves there who had already died once... and that they had missed words like "grave" being added to the language. 

I got tears in my eyes when they found the little boy. I had hoped for a happy ending but, of course, this is Alqualonde.

This was powerfully written, and I loved the complex emotions here especially:

"This wasn't supposed to happen here," Ëassalmë said as they lowered Ellindo's shrouded body into the grave. "We were supposed to be safe. They promised we would be safe!"

Minyelmë gazed up at the Pelori, towering over them. They were meant to keep monsters out, but the Valar themselves had released Melkor from Mandos, to sow his seeds of discord—and Minyelmë had no doubt that he was at the root of all of this, not only the death of the Trees but the strife among the Noldor that preceded it—and in the end death had come not from without but from within.

They are, ironically, echoing Feanor, who was (in my interpretation) driven to his deed because, of course, he suffered twice over what wasn't supposed to be permitted at all in Aman and was left an orphan. It makes me wonder what will be the outcome for them--for all of them--who remained behind in Valinor.