[Legolas]

Well said, Formendacil.

Originally Posted by Raynor

Your quote is misleading. It reffers to the ability to pass over to the west, not to his immortality.
It wasn't just sharing their fate, but also their other abilities, which I mentioned previously.

I think his fate is implied. The fact that he shares their abilities remains unchanged by his fate. He would share their abilities in any event. Imagine that he never receives the choice. He eventually dies as he is mortal, given Manwe's judgement. His nature is due to his ancestry and environment, not his fate.

He lived the life of one, therefore accepted in his community as a full Elf.

He is not accepted as "a full Elf" and has no need to be. He is accepted as himself, Elrond Peredhil. Half-elven, and of the lineage of Finwë, Thingol, and Melian. Socially accepted among the Elven, and they are all aware of his family more than anyone. They know the story backwards and forwards. Why does he need to become anything other than Half-elven?

Likewise, Gimli "lived the life of one" on Tol Eressëa, but that does not change his fundamental kind. He is a dwarf, and accepted as a dwarf.

It wasn't just sharing their fate, but also their other abilities, which I mentioned previously. Anyway, do I understand correctly that you consider Men, Half-Elven and Elves to have the same "blood or genetic makeup"? If so, what would make a Half-Elven less of an elf, than a "naturally" born Elf?

They must be of the same genetic structure, but not the same genetic makeup. By genetic makeup, I mean the specific genes passed to him by his parents. Just as native Africans and native Europeans have the same genetic structure - they are H. sapiens with 46 chromosomes - but do not have identical genotypes.* The offspring of a native European and a native African will be less European than a "full" European, and less African than a "full" African - yet any one offspring has the chance at being much more phenotypically† one or the other.

Which actually brings me to a better description. Elrond's phenotypes are all, or at least more often, Elven where there is a difference between Men and Elves. However, that does not change his genotype. He is still Half-elven.

It may be even logical to presume that this is why he chose to be immortal - he was more Elven in manner, felt more connected to that aspect of his ancestry, etc.

* genotype - an organism's genome, or genetic makeup
† phenotype - the actual characteristics expressed as a result of genotype and environment