"Preserving the divine light of Valinor so we could live outside it. Making it possible to talk instantly with anyone anywhere in the world. Armor like mine, which -" he smiles bitterly - "is enchanted so thoroughly I am almost impossible to harm in battle. Besieging a god for four hundred fifty years. Inventing new chemistry and biology along the way so we could figure out why Men died so easily, inventing music and fortresses that let us stand against a hundred times our numbers..."
"You can die and therefore you are a mortal. If I had sorcery I could de-age somebody every fifty years but they could still die and they'd still be mortal."
"Yes, because if they did die they'd be gone, that's it. Whereas we just are stuck without a body until we can get a new one, which you yourself said might be what happens if you were destroyed in a way you couldn't heal from. If I figure out how to actually properly stop existing then it'll be correct to say I'm mortal. The Eldar in general still wouldn't be."
"I don't know what would happen if there wasn't enough of me left to heal but I definitely would remember if I heard of bodiless fairies being a thing."
"I'm also quite sure I can't stop existing. New body elsewhere might be it." She smiles a little. "Maybe I'd wake up in my tree."
"You'd have to get someone else to do it. And I'm not confident at all, I just made that up. But I started with common knowledge and some of it is that I will never, ever die."
"Same principle. It's all the same. There are maybe fuzzy areas - mental sorcery typically counts as harm but read-only telepathy might not if I were thinking outside my tree; you could maybe turn me into an animal if you were a sorcerer and I wanted to be an animal; but you can't hurt me."
"It's not about what's 'experienced as' harm. There are plenty of things whoever's got the upper hand in a mutual vassalization can still do to their vassal. I don't know what use of osanwë you have in mind but communication probably doesn't cross the line."