[throwGuardian]

Guessing such a rule helps in duplicate submissions detection. But, that should be possible from checking the URL.

Unless one uses a link shortener. Are shorteners permitted on HN?

[grzm]

Nope. Some sources, such as Medium embed viewer-dependent identifiers in the url which can confound de-duping based on URL alone. I don't know if 'dang et al have figured out a way to handle these cases.