Footnotes are mainly straightforward-enough glosses and references, but there have always been digressions (and quite often sniping) in there too. The C19 has some real specimens.

I like footnotes, or in this case maybe we should call "endnotes". David Foster Wallace was known to use them a lot, sometimes he would put footnotes in footnotes.

Good old postmodernist literature. So meta.

Whereas legal opinions use them either as a citation dump (known as “collecting cases”), as a place to bracket issues that are not being decided, or as a place to put a substantive response to a separate opinion in the case (if you’re an appellate court).