The thing about gamification is that it steers users towards maximising some metrics: they will change their posting behaviour according to the rewards.
Anecdote: I recall with G+ I found I changed my posting style when I started to get more than 10 likes on a post (I’m not famous!) - I would feel better when I made posts which got more likes, I would feel worse when I got fewer than 10 likes. I changed my style, posted about different things. I was no longer acting according to my interests, or trying to communicate anything particular, I was trying to make popular posts. And with no reward other than likes.
This will suit some people and some communities, but not me.
Yes, there is an official plugin