There are two noticeable differences between the optimate/populare and the traditional left-wing/right-wing politics:

1) Traditional politics is much better approximated by a binary. Person’s views on one significant issue, such as feminism, pretty accurately predict positions on foreign policy, economics and environmental issues. By comparison, optimate/populare labels have much less predictive power. While there is a significant correlation between populare (optimate) and left (right)-wing views on economics and foreign policy, both optimates and populares are much more likely to cross ideological lines on individual issues.

2) On average, both populares and optimates are more libertarian and less religious than the traditional left and right.

If the number of extended discussions is uncorrelated with the post's karma (except maybe for strongly downvoted posts), and the number of extended discussion comments dominates the number of total comments, then that is evidence that correlations between the number of total comments and the post's karma are spurious.

If the number of extended discussions is uncorrelated with the post's karma, then they would simply add a random noise component to the graph. I think it’s pretty obvious from the graph that the signal to noise ratio is quite high.

That would require a non-trivial amount of work. Is there a particular reason you are interested in this?