Why not make the replay button go to a public reply automatically and make people use the drop down for private or whatever. I'm sure people will figure that out.
And as you're undoubtedly aware, we are a people of icons and images because of the internet. Most people under 65 now know that a star means favorite or followed. One color for favorite, one color for followed. The icon self explanatory.
Eliminating redundancy is an art without confusing people. Like a road sign with a right curve arrow with the word 'curve' over it. I'm sure people will figure out your symbols as well.
Well ,maybe not maga's, but they shouldn't be allowed on library computers in the first place.