I could honestly not care less about single-word posts containing a generic +Agree or -Disagree for the same reason I couldn't care less about single-word posts containing a generic -+Support.
If empty yes/no responses are all that are needed to pass a vote or suggestion, why not just make it a poll? If you want to elaborate more on the subject or the reasoning behind you answer, then just do so right away; anyone reading it will understand by your post what your opinion is. If you've already elaborated, then you could toss a quick coloured -+Opinion in there so people can see your verdict at a glance if they're just skimming through the thread.
tl;dr: people who post nothing but -+Opinion are not credible.