The markup for @-tags is poor. No class labelling for the list of tags, no spans to distinguish the different tag constituents, no class to target/distinguish the different tags

Contrast the markup here:

https://docs.mirage.io/fmt/Fmt/index.html#val-set_utf_8
https://b0-system.github.io/odig/doc/fmt/Fmt/index.html#val-set_utf_8

or here with a few different tags like @since, @deprecated (note the @raise is not used there though)

https://docs.mirage.io/ocaml/String/index.html
https://b0-system.github.io/odig/doc/ocaml/Stdlib/String/index.html

Also In general I'd move away from dl for lists of elements: they are harder to style than it should be, because list elements are made of two consecutive blocks of elements rather than a single element. It's much easier to style li elements with properly spanned and classified elements.