Currently, in the linked/related sidebar, without opening the question the user can only distinguish whether the question has an accepted answer (green icon) or not (grey icon).
I often eagerly open an interesting-sounding question with a grey icon, only to find myself disappointed because it has no answer yet.
To avoid this, I suggest adding a third type of icon for questions that have at least one answer, but no accepted one. Probably a darker/lighter icon or some kind of frame or glow. I've made a quick example with Paint (if relevant, the screenshot I used is from this question). I'm in no way satisfied with the look of it, but at least it demonstrates the general idea.
What do you think about this proposal? Would it be a useful addition to the StackExchange interface?