#and weren't done for any reason other than cathartic revelling in cruelty

[madtomedgar]

i think it is actually possible to do an interpretation where 

a) nie huaisang never actually knew about the altered song of clarity,

b) the altered song of clarity had no real effect, or

c) both at once.

So. A. How Nie Huaisang knows about the alterations is never addressed. I’d argue it’s not actually necessary for his motivation or revenge plot. His brother has been insisting for years that Jin Guangyao is up to no good, can’t be trusted, has gone too far and must be killed, will die if he doesn’t bring him Xue Yang’s head in x amount of time, etc etc. He has also violently attacked Jin Guangyao in front of Nie Huaisang multiple times. He dies, as far as Nie Huaisang or anyone else knows, of a qi deviation brought on by big sword brain disease. And Nie Huaisang doesn’t take this well. Nie Mingjue’s condition is aggravated and accelerated by anger, and the people who make him angry consistently are Jin Guangyao and Nie Huaisang. Nie Huaisang has a vested interest in downplaying his own potential role as a catalyst, and in forgetting that this just happens to the men in his family. And look, was it really his fault that Jin Guangyao was always bringing him presents and encouraging his actions that made his brother angry?? And idk I feel like it’s an easy slide from “If Jin Guangyao hadn’t made him angry all the time/made me make him angry, he’d still be alive” to “Jin Guangyao made him angry/made me make him angry on purpose to kill him faster.” Since Jin Guangyao was also (supposedly) treating Nie Mingjue’s condition, it’s an easy slide from being mad at Jin Guangyao for failing to keep Nie Mingjue’s condition in check to... deciding that he could have if he wanted to, and the fact that Nie Mingjue is dead means Jin Guangyao must have killed him. Of course he eventually finds at least either Baxia’s ghost or the severed arm, which confirm to him who, but not how.

And B. So Nie Mingjue is dying anyway. Clarity is palliative. He doesn’t seem to be doing anything else to manage or slow his condition, and in fact, he seems to be engaging in activities that aggravate it. He is also paranoid about, and obsessed with, Jin Guangyao, and specifically Jin Guangyao engaging in underhanded and devious schemes against the Nie sect for his own gain. He also infamously is tone deaf. Because there is textual evidence that Jin Guangyao did alter the Song of Clarity, he can’t have actually made it up wholesale while chilling on the shelf. Though it wouldn’t be out of character. But it doesn’t need to have actually done anything, or much, for him to end the way he did. I also will point out that even though Lan Xichen revokes Jin Guangyao’s access to the Cloud Recesses after he finds the missing page, he then goes with him to bury Nie Mingjue, address the burial mounds situation (which he knows is sketchy) and then stays with Jin Guangyao when he’s injured. And while this could be evidence that Lan Xichen is conflicted in the face of both overwhelming evidence and his 20+ years long relationship with Jin Guangyao, it could also be evidence that what he found when he tested the song was inconclusive. 

So like... if you want to get really deep into the JGY apologism conspiracy theories, this one isn’t... the wildest.