Code:

#!/usr/bin/env ocaml

(* ... *)

Error:

ocamlformat: ignoring "hello.ml" (syntax error)
File "hello.ml", line 1, characters 0-3:
Error: Syntax error

Judging by this StackOverflow post recommending preprocessing the shebang away with sed these things are not super welcome in OCaml community. Github search returns a number of examples, some of them including the top-level directives like #load which trigger the same syntax error. I'm too new to be sure if these examples fall under the TOS listed in the readme ("OCamlFormat requires source code that meets the following conditions...") . Preprocessing the thing away with sed would require to stitch it back on again :)