While writing a blog post about the new website backend, I wrote some markdown that used the same footnote twice. I noticed that this resulted in a duplicated footnote, which is not what I want. Looking up the problem, I find jgm/pandoc#1603.

Apparently, this is a fundamental design issue with Pandoc's AST and has been open since 2014, so I cannot expect it to be fixed anytime soon. However, it appears that the main hangup about fixing the issue is that changing the AST will affect a lot of users, so they don't want to change the AST very often.

A footnote is just a Note [Block], so there's no way to work backwards to find out which footnotes were actually the same. However, I think this is only a problem if I have footnotes that have the same content but different footnote IDs. I don't, so I think I can work around the issue by de-deplicating the notes by their contents.