If I write code like this:

(* $MDX part-begin=something *)
type t =
  | Foo
  | Bar (* $MDX part-end *)

Then what shows up in the MDX is:

type t =
  | Foo

This cuts off | Bar. Granted, a solution is to always put the comment on a separate line. But ocamlformat doesn't know this, for example. It would be better if mdx always preserved all the code between delimiters.