I was referring to something different. For example, in this topic, you posted a response that the OP marked as a solution, so it bears a big green checkmark, and it appears right below the original post, even more prominently than an accepted answer in a post voting topic.
But I agree that the little checkboxes on topic listings are inadequate. Earlier, I also made the point that, in a post voting topic, the 
buttons beside the question act as a placebo – they don’t influence the listing at all.
That’s true, the solution plugin is orthogonal to post voting. For example, this topic has both post voting and a solution that the OP picked out. The analogue to post voting in a normal topic would be the 
button, which apparently shows only the posts with the most reactions. I don’t know if that’s intuitive enough for new users; it probably depends whether they’ve had more experience on Discourse or Stack Exchange or neither.
At one point, it used to be possible to both upvote an answer and give it a 
emoji, like the one I just gave your comment. That was a bit confusing, though emoji reactions have since been disabled in post voting topics. Those who chose to react instead of upvote – joke’s on them.