Yep, it is: if you view the csv with the original scraped data, you will find the rank of submissions is at most 30. (Also, you would never get average point scores upwards of 20 and 30 if all submissions were considered. And you were probably posing a rhetorical question, but heck, I'll answer it :)).
It is possible that more interesting articles are posted in the afternoon due to the work habits of the people who actually create the content that is being linked, and posts linking these articles happening in a short time span.
It may be possible to correct for this by only including links that are for content that was already "old" at the time of posting?
While there's no doubt that some times are better than others to submit, I think it's best not to abuse this to get karma. It's nice having at least a couple hour window where self-submitted blog posts from members of the HN community have a chance to make the front page, but this goes away if people are spamming the system with random stuff.
The article is average points and comments based on submission time.
Appearance on the front page is a relative thing depending on the scores of the other articles. So if 20 articles all go through at "peak" submission time, nobody goes anywhere.
This is interesting. The thing that jumps out the most to me is that there's definitely not an order of magnitude difference. Thus, I don't think when you submit your story should be a concern. Quality and relevance have much, much bigger impacts.
