Interesting stuff. It's a bit unfair to talk about this animation/roto work as "black marker." These were meant to be invisible fixes, and most of them worked - I never noticed any of these until you pointed them out. (In fact, I never noticed the Emperor's slugs before they were pointed out to me, either.)

It's certainly better than some other optical-era roto/matte fixes, like when they had to block out Coca-Cola signs in Grease because the producer had inked a tie-in deal with Pepsi and the set dresser didn't know about it.