[kkoncevicius]

I think HN temporarily brings newest posts at the front so that someone who checks for new replies can quickly find them on the top. After a while they are moved to the bottom. I am not sure on the exact mechanism behind this but observed it multiple times. So the "posted 0 minutes ago" part in your observation is telling.

[gus_massa]

I agree. The order of the post in the front page is something like upvotes/(time in hours + 1)^1.6, where the number 1.6 changes from time to time without warning. Assume it is something between 1.5 and 2.

One upon a time, the order of the comments used the same algorithm. It is not clear how they are ordered now, but I assume that it is something similar.

Both orders are also affected by penalties, a lot of penalties. Some are automatic, like some keywords, or domains, or if a post has much more comments than upvotes. Some are added manually by the mods (or removed). Some are added if too many people flag the post. Just assume that there are a lot of penalties.