I think the tradeoff there is that the HN submitter crowd are very fast to the draw. I'll often encounter a story elsewhere that I want to hear from HN about, so I'll do a search and find it was submitted 15 minutes ago, or even days ago (and I wonder what RSS fueled craze people must go through to find and post things so fast). Of course, for me those are the best cases, because I can go through and read what people think and reply without having to wait for the uptick. But no karma for the slow.
I do agree with your point, but unfortunately I was limited by what is available from the APIs: the upvotes for the comments were not provided. I couldn't find a proxy for it either. Thus, I couldn't include it in the analysis