For 2, I'll single out the skill of tailoring technical explanations to your counterparty's level of understanding and technical knowledge. The ability to explain to less technical people what your new project/feature does without going into too many unnecessary details and without being too high-level is invaluable. It builds confidence in your work for them (I know what this thing is doing - maybe not all nuts and bolts, but enough to operate with confidence) and in you as a professional (this guy clearly understands what he's working on and does not try to bury me in jargon or oversimplify things).