Any kind of plumage is larping, any non-functional horns, antlers, feathers, etc. Animals waste a large amount of resources on these and frequently avert death matches this way.
I was reading recently about fish that larp as female to swim beneath the fighting males and impregnate the females (I believe Russell Brand mentioned a similar tactic, though without the intent to pass on his genes).
Strange, I heard from Asatruar that Divination is for Women, so a man doing divination is frowned upon but Magick is for men because it is active. Seidhr specifically though is considered a female thing, but Allfather Odin is also a master of Seidhr (he gets insulted by Loki for this reason), and throughout history men also learnt Seidhr despite the cultural backlash, but I don’t think it harmed their relationship to the Gods. Rune magick, however, is a far more “male” thing, many men in the Sagas and the Poetic Edda learn Rune Magick without an issue. Seidhr has to do with divination so that’s why that is considered a female thing, but Rune and Galdr magick is active so it’s considered a male thing. Of course, these magickal gender roles are just buckshite from reconstructionists that want to roleplay.
She specifically taught him Seidhr, Rune Magick was always more of a male thing. But Odin is also a master of Seidhr, so yes he broke that cultural dogma “rule”.