I think there's a lot of useful criticism of arguments that falls outside this hierarchy. You can attack an argument without ever disagreeing with it, such as

I think there's a lot of useful criticism of arguments that falls outside this hierarchy. You can attack an argument without ever disagreeing with it, such as by challenging its interestingness or applicability or its relevance to the rest of the discussion. Where does this comment fall in the hierarchy? I think what's really going on here is that the hierarchy isn't actually a hierarchy. In a proper hierarchy, each level should necessarily entail the previous. Here DH1 entails DH0 (I call DH0 "ordinary ad hominem" and DH1 "circumstantial ad hominem") and DH6 entails DH5 entails DH4 entails DH3. But DH2 has nothing to do with any of the others, and DH3 has nothing to do with any of the previous.