Deleting my account now, this is getting ridiculous.
One is hacking at a compiled code that is not well documented, and talks about the subject.
The other is a mod, for a well documented game.
Because audience of Hacker News forums found it interesting and upvoted it.
Why did people upvote it? I imagine because rather than just being a link to a downloadable mod, it is a thorough diary/article on how a person researched, developed and implemented the hack. Precisely the kind of article HN tends to enjoy - regardless of exact subject: restoring old Xerox machines, creating a LEGO robot, etc.
Rather than just colour shading, I think it's also fascinating they decided to remove / modify the bloom - one of the defining characteristics of DX:HR for many people.
HN readers in general have a wide range of interests - example: 73 points, 62 comments on a link to an article on the history of Macaroni and Cheese: https://news.ycombinator.com/item?id=22951281
On-Topic: Anything that good hackers would find interesting. That includes more than hacking and startups. If you had to reduce it to a sentence, the answer might be: anything that gratifies one's intellectual curiosity.
I don't know what constitutes a good hacker, exactly, but I thought it was interesting.
Having read your comments before I read the article I was expecting something much more simple.