I believe the parent is talking about submitting links to websites that render their content via clientside JavaScript and how that would break the hash dupe de

I believe the parent is talking about submitting links to websites that render their content via clientside JavaScript and how that would break the hash dupe detection. They aren't suggesting that the functionality would need to be implemented in JS by HN. Regardless, hashing the content to detect dupes is just an idea that wouldn't work for a lot of reasons.