Back to eyebrows: would you believe they actually acknowledge this on starwars.com on the episode page?!
“Although the final cut of Return Of The Jedi has an eyebrow-less unhelmeted Darth Vader, to better read in animation, the animation model has the dark brow visible through the cracked helmet.”!
I just watched the finale, and was so excited about the eyebrows that the first thing I did was open up this thread and search for it. Maybe these dumbass changes will slowly slip from the grip of canon.
The creators said the only reason they put the eyebrows back on was because the character model looked really dumb without them. It was only artistic and does not change the canon.