I've seen probably 2-3 dozen HN redesigns through the years and this is probably my favorite (in terms of potential). The primary mistake most of the other redesigns made was that they tried to increase the whitespace to make it "prettier". The main issue was always that the information density became much higher, which led to unnecessary page scrolls to view the same information one can view today without a scroll.

A few critical words -

1) Without showing vote/flag/etc buttons, it is hard for me to imagine the usability of the design

2) The #1 issue at HN is "no support for mobile" - this does not address that

3) The #2 issue at HN is "nested comments". Your design does not seem to address this at all. For example, let's say that you don't like the first three comments on a big story (http://hacker-news.xyz/story/9983204). How many scrolls before you reach the 4th?

Overall I like it!

This looks great! I really like the use of color to indicate upvotes.

One thing I'd love to see is the domain featured more prominently (either in a darker font, or positioned under the article title, etc.).

Not mobile optimized? Has to be HN :-)