Something I worry about: is how any position that is not extreme will get invariably get “primaried” by those with more extreme positions in any online debate. 

They will attract more energy , easier to get social capital and also plays well to most online algorithms. 

Having the center get and hold energy seems an unsolved problem.

To fix this, we need more actions. 

Right now the only actions on social networks are "words" - which leads to the phenomenon you describe.

As an example, imagine if algorithm took, as input, "financial contributions to XYZ." My guess is that while ppl might give "likes" to extremism, its not where they give money.

This is one of the big potential unlocks for blockchain-integrated social, imo