RE: Does Punishment Produce More Cooperation?
People's behavior isn't always purely selfishly motivated. For example, despite the impending danger of a fire, instead of saving themselves, someone can take the time and risk to raise a fire alarm or even help others to evacuate and get out safely. We often favor cooperative behavior over selfish behavior.
This is not the only way to interpret "selfless" behavior. Sometimes people do things for others because they know they wouldn't be able to live with themselves if they didn't. In that case, it's inherently selfish to help others.
It seems like the alternative dilemma scenario you describe combines Nash Equilibrium with the Shapley Value into one game. I go into those and how I think they relate to Steemit in my article called Game Theory and Steemit.
Purely selfish, as in with disregard for others, or at other's expense, without consideration for others, etc. Indeed, selfishness with respect to being inclusive -- of recognizing the reality that we are not being/existing on an island alone -- will motivate people to be more inclusive of others to amplify their own well-being and ability to receive benefits from others. I'll check out your post, thanks for sharing and for the feedback :)