Maybe the solution isn't adding more UI but just making the icons more descriptive.
Yeah, I'm pretty sure people mouse over the icons to see what they're about, but I usually find myself going straight to threads that are bold, regardless of what the icon states. My brain just doesn't process a dot/semi-filled dot/empty dot immediately, though I am getting used to it.
My suggestion was mainly for newer members, not so much for old btw.