page content hash

Change one byte.

  regex match

Now we get into ship-of-theseus arguments. What counts as the "same" article? 99 percent? 51 percent?

What if you resubmit a blog post that's picked up 150 more comments since it was last posted? How would HN tell the comments apart from the article text?

What if someone submits a blog post that heavily quotes another article that's been submitted, in the process of rebutting it, and ends up being a 80% match?

What if you include the full text of moby dick, in a display:none <div>? What if the page loads the text of the article with javascript? Would the HN submissionbot have to render CSS and javascript?