Very interesting thoughts!

Tolkien himself might perhaps agree with some of this on some days. At least, some of it sounds a bit like that letter which accuses the Elves of being tendentially "embalmers".

Jackson's Elrond has been criticized a fair amount by fans in the past for not being "kind as summer" and unlike book Elrond in this way. That is is not to say that Jackson was not drawing on some of book Elrond's traits there, in his own way. But I am still struck by how much you are making movie Elrond the crown witness. I read the book a long time before seeing the movie, so for me, personally, those two Elronds are very distinct.

Book Elrond is hardly infallible either, though. And it is true that he sometimes gets airbrushed into angelic rightness. Although I have also seen him attacked for being too Noldorin!

So: on some days Elrond is kind like a 35-degree heatwave?

My family really struggled to conceptualise the descriptor "kind as summer" too, since summer in our context is quite ambivalent. It would signify: exhaustion, frequent unrelenting heat, risks of heatsickness & sunburn, and in some senses reprieve and joy (holidays, days in the cool waters of the beach). It was interesting to turn the struggle of understanding this phrase from an English/European standpoint, to how our concept of Summer might create an equally valid interpretation of kindness. 

I really resonated with your idea of a flawed Elrond. This guy is carrying a fair bit of trauma... he's going to be dealing with that, and that's got to shape the way he lives his life. The idea of a flawed Elrond, I think, doesn't at all detract from what his character achieves within the narrative, but makes it more meaningful. It is quite hopeful, is it not, to have a figure that deploys his kindness and care with flaws and failures, and yet still largely succeeds in the creating the better conditions for the next generation than his own? To know that there are harms there within the kindness, doesn't negate the good it does either, but makes it something we might also hope to achieve. 

On the aesthetic dimension of kindness as being legible as goodness: there are some quite interesting implications here for how we judge other characters too. Thinking of Finrod, I wonder if this is why readers may find it so easy to overlook the thornier implications of his own oath to Barahir and the position it puts Nargothrond in. He has the right aesthetics and so we can gloss over those. In the Prayers to Broken Stone universe too, kindness & goodness are frequently not coming under the aesthetic that would be legible to us straight up as such, or kindness is complicated with harm. Someone like Celegorm wouldn't be easily read as kind/good, but his actions do reveal some amount of both. 

A fantastic view on a character that often gets a pretty monochromatic portrayal, and you’ve done it in a way that invites a deeper reading without accusation, which is difficult to execute.

I was particularly struck by the narrative “tone” that Elrond exhibits, as calm and soft-spoken and how that is often an extremely culturally-dependant attribute, positive certainly in much of the west where speaking in a louder tone or showing passion often might get perceived as “angry, violent, unrestrained.” Tone of course, as you demonstrate, has very little to do with “goodness,” and it ends up being a completely false correlation.

This here too:
“But more significantly, he is positioned as a carrier of memory, a living archive of sorts, tasked with both remembering and also holding, curating, and transmitting the aftermaths of war, loss and failure.”
Very, very observant! And this is such a unique role Elrond plays, he IS the memory of Middle-earth, a role that seemingly even older elves, such as Galadriel, Celeborn or Círdan do not take. This made me think quite a bit on Galadriel’s mirror and how she often restrains from offering council - when asked for council by Frodo, she re-directs the task to the mirror and refrains from her own reading of what it shows. To carry memory of course is to curate it, to decide what goes in and what goes out, like a museum, an almost guaranteed partiality.

“It treats historical violence as something that can be ethically settled by a perceived moral arbitrator, rather than something that continues to press upon the present in ways that remain unresolved.”
Nothing to add but only clap to this, so aptly put.