The idea that only zaps are quality signal is dumb. 

This is like ignoring the vast majority of people who don't want money in their social interactions. 

Imagine standing in a circle of friends and zapping each other 2 cents every time someone said something you agree with. This is just not how social interactions work. Money was never part of the social agreement. 

Proof of work and all / actions speak louder than words / put your money where your mouth is... I get it, that has value and is absolutely true in other context, but not in social. It's a nice bonus, it's great to be valued with a payment for something you put effort into, but it can never replace free expression without the expectation of payment. Believe it or not, some people don't want money involved in their conversations. 

That's not to say that you can't have it, but don't insist on only zaps. It's going to turn people away.