Severitus number at least 7
Severitus where Harry has hsd (hyper mobility spectrum disorder) and he doesn't know. Like, his knees are hurting, he's randomly falling and manually taking every step. His elbows hurt, his shoulders on fire, he can't sleep. His back cracks constantly, everything hurts, and it feels like he constantly has to hold his body together. Well, one day it starts affecting his hands/wrist and he drops his wand or something. Snape makes a snide comment and Harry somewhat explains. "Professor, I'm sorry, but it feels like my knuckles are on fire and they're really hard to control today," or something like that, and Severus is just like 'uhhhh, tf? That's not normal.' He tells him to stay after class or wtv.
Add ons to the trope:
Madame promfrey doesn't really believe it's that bad, says he needs more sleep, etc. Severus yelling at her to get him some actual diagnostics, telling her that this isn't normal and that he needs help.
Harry is sobbing because it hurts so bad and nothing he does helps. Everything is on fire and it's so painful, no one can touch him without it hurting. Severus just nods and talks to him maybe combing a hand through his hair, trying to help him stretch his muscles, giving him potions to relax his muscles. Maybe, if there's a calming down point in the flareup, he holds him while he sobs about how much everything hurts. No venom, no comments, just support and listening.
Severus is the one to do research because we all know he secretly cares. He learns that the pain comes from the muscles tightening around the bones, learns how to help, learns how to get him to stretch his legs, shoulders, etc. He's the one who has to tell Madame Pomfrey to give him a muscle relaxer. He's the one to stand up for him whenever he's in trouble for it.
Ron and Hermione may not like Snape, but whenever he's having a bad night. Maybe he can't move, maybe his sobbing, doesn't matter, they go to Snape to help Harry, and he does it without complaining. He just silently nods and follows them.
Harry is unable to do housework for the Dursleys because it hurts too much, and Severus gets a letter about it from Harry. He talks about how unfair the punishments are— fucking casually mentions abuse because like, he canonically does it, lol— and Severus scolds them.
Harry shows Severus all the 'cool tricks' he can do with his body like rolling his eyes back to be white, dislocating bones, stretchy skin, etc, and Severus being horrified.
Severus knowing EXACTLY what causes a flare up. He knows quidditch hurts, but he won't tell Harry to quit because it's the one time he feels like a normal person. He knows that DADA hurts sometimes. He knows that duels hurt like nothing else, and he never judges. He never tells him he shouldn't do it because that's cruel, Harry just wants to feel normal for a moment. Severus holding him and supporting him through the flareup.
Severus absolutely babying him during flare-ups, although he'd deny it if anyone asked or if Harry told anyone. Like, he's cooking soup, helping him brush his hair, helping him get up, write, etc. Like, he's just completely there.
Severus never stops Harry whenever he talks about the pain, no matter how many times he's heard it, no matter how many times Harry tells him his knees hurt, no matter how many times he says he feels like he's going to puke because of the pain. He just nods and listens.
