I love this question, on many different levels, but will only address one aspect that I haven't seen addressed here yet.
I'm a high-school math teacher, and try to find topics in my classroom that will engage/surprise my students. Voting theory is one of those topics. It turns out that there are different ways determine winners when there are multiple candidates, as well as different rules for voting – everyone may cast a single yes vote (or no vote), or everyone can be allowed two or three or many yes (or no) votes. In a vote between two options, the outcome is pretty much the same no matter what system of voting or tallying is used.
However, when more than two options are present, things get much more complicated. For example: should we spend our time on (a) direct ancestors, (b) collateral relatives, or (c) improving documentation. My answer would be yes! they are all important. I could upvote all three because I think they are all important. But perhaps I think the most important thing we could do is get DNA samples from more people, or record interviews with our elders. A downvote to all three of the topics could show that I think something is missing from the options presented.
But what if I thought all three were important, but that improving documentation was what WikiTree really needed right now; or I felt that all three were important, but that we were already doing exceptionally well when it came to documentation. This is when things start getting interesting in voting theory. The "winner" in an upvote system may actually be the option that the majority of the people think is the worst option, and the "looser" in an upvote system can be the only option that most of the people would be satisfied with.
Sometimes, having a downvote option can better represent the position of the "majority" better than an upvote system. Having both options... well, people who don't like a solo-system (up or down) may prefer that to the alternatives.
I know this doesn't deal with the emotional impact of having something downvoted, nor with the desire for feedback so we can improve, but my students find it fascinating – especially when they realize that "splitting the vote" can ensure that the least favored candidate will win.