Since ThunderClan is so into big muscular bodies and fighting prowess, imagine them having this big Scar-Off, trying to out best each other with old battle wounds. The weirder the place, the bigger the scar, the more likely you are to win.
Cats being like, yeah, Bramblestar, your shoulder scar is decent, but every warrior has gotten biffed over the shoulder before.
Dovewing has scars all over her arms from blocking blows to her delicate ears, so her ears are one of the few sets in the Clans lacking nicks or anything while her front arms and paws are missing fur and are otherwise ravaged. She gets a bunch of yowls and cheers as she proudly shows them off. Jayfeather’s side slash is pretty average, but he gets a bunch of support because he’s not a warrior.
The queen of scars in ThunderClan is, of course, Ivypool, who’s almost always got a new one to show off. Blossomfall is her hype warrior as she struts to the center of camp (”ooooooo ya’ll are you ready for the ‘pool I don’t think ya’ll are ready for the ‘pool”), glances around to make sure she’s got all eyes on her, then hup! she’s balancing precariously on her back paws, displaying a near-lethal belly scar. The Clan goes wild- pun intended.
Then, out of the elders den, comes Brightheart. She’s one of the few who doesn’t really get into these things, but today she goes up to Ivypool with pride, showing off the half of her face horrible destroyed by the dogs. “I think I win,” she meows, a bit shyly.
Ivypool over-dramatically falls onto her back, wiggling her legs. “Noooo! I’ve been defeated!!!”
(”She wasn’t ready for the ‘heart,” somebody whispers)
Just… I dunno. ThunderClan turning bad memories into symbols of their ability to live and thrive. And even if a cat doesn’t like showing off, at least they know that there will always be love and support coming from their Clanmates.