The link is updated to reflect the following
After SeanDav's question and minimaxir's comment, I summed up reposts' scores before computing the mean and the median:
HN news sources by mean score: https://docs.google.com/spreadsheets/d/1tTDDG2xg7OVKdUy4WCZ_...
HN news sources by median score: https://docs.google.com/spreadsheets/d/1P20sKg-fI6msZVZtJFe0...
HN news sources by number of submissions: https://docs.google.com/spreadsheets/d/1mmfbNWaX0Nr1P65VmwZp...
SQL code: https://github.com/antontarasenko/smq/blob/master/hackernews...