Because comment sections are not good measures of opinion - they are places for discussion. People make more effort to engage if they have strong positive opin

Because comment sections are not good measures of opinion - they are places for discussion. People make more effort to engage if they have strong positive opinions and minor negative opinions. Minor positive opinions, which (you hope) are the average in an audience, get unrepresented if the effort required to give feedback is great. That's why metrics measuring average opinion - like NPS - aim to require as little effort as possible.