@Zylann No, not this time, although that is a sneaky one. My camera doesn't move in my test scene. The jitter is mostly caused by the objects being ejected from collision resolution. The best result I could get was by using a capsule with enough thickness.
For other problems I offset the slide angles on slopes and modified gravity, etc. Reduces a lot of the problems, but doesn't entirely eliminate it. I'm thinking the RigidBody is not the way to go for characters in platformers, or maybe I'm missing out on some fundamental tricks.