Ask HN: How do I submit a page that has been updated?

I tried to submit a link to a page that has previously been discussed here on HN, because the content of the page contains an interesting update. No matter how I tried to submit it (appending a bogus query string, and a couple other tricks), the posting screen just said "invalid/expired link". I'm guessing my tricks didn't work because whatever fetches the page content uses the `rel="canonical"` tag value to normalize the URI.

Anyway, what's the deal with this rule? Pages change over time, how come they can't be resubmitted? The page in question, as well as the HN discussion, are over a year old, for what it's worth.