Thank you for considering that. Mind you, I'm just trying to give constructive feedback here for I value the site and I see that it can be greatly improved by this considerations (IMO as a user).
Possible badgifiable metrics for quality of contribution could be:
  • For Posting: ( post_total_stack / number_of_posts )
  • For Commenting: ( comnt_total_stack / number_of_comnts )
Possible badgifiable metric to measure retroactive engagement could be:
  • ( total_spending / number_of_answers ) ; number of answers given to posts or comments