Pretty near and dear to my heart. We actually resolve every link that you put into the submission URL form into its canonical tag as to avoid people submitting the same thing twice. Yet this still often fails sadly, for various reasons that are not only bug related, but because often people set the canonical tag falsely or to the root of the domain. We even have domains where we won't respect the canonical tag because it's set wrongly, rekt.news and hey.xyz xD: https://github.com/attestate/kiwistand/blob/b6d58ac4ea214ddc949174d01f9444ca668eb681/src/parser.mjs#L92