I have to say I've never seen the point of the "disagree" or "eye roll" buttons unless they're followed up with an explanation of why the poster disagrees.
In most cases, anyone following this thread knows whether any of the regulars in the thread are likely to agree or disagree with particular points, after all, and I take the view that, if someone happens to be interested in the fact I disagree with something, they're probably more interested in why I disagree with the point than in the simple fact I do, possibly because they think they may find particular facts or lines of argument that I advance might be useful when the contentious point appears elsewhere.
So if I see a post that makes me roll my eyes, I tend either simply to ignore it or respond to it, as politely as I can.
Though politeness can, of course, create its own misunderstandings