Mod-42,
I don’t understand those who deliberately do not stand. As you wrote it is unclear whether Kallah domeh L’Malka, and it is certainly clear that Chazal gave a Kallah tremendous import and Kavod. It is well established that standing up is a sign of respect and kavod.
At the very least there are respectable grounds for the minhag of standing, so why would some people be porush from this minhag?