I doubt that people on HN would be motivated to write better comments on the off-chance of earning an extra 70p. I also doubt that people on HN would be willin

I doubt that people on HN would be motivated to write better comments on the off-chance of earning an extra 70p. I also doubt that people on HN would be willing to tip the sort of money needed to motivate other people on HN to write better comments. You run the risk that people who don't attract tips will give up writing comments altogether.