So about the only reason I have for it is some certain parallel algorithms I'd love to use, that are mostly best done at the thread level.

But, these days using unix sockets with some cute flags letting multiple proceeds binding to the same listening sockets means it's sort of less needed!

Though, doing a lot of work with Nim lately and exposing thread pools via Futures makes for some pretty lovely easy parallel code, so I dunno. Not a deal breaker but a nice to have, and having threads in OCaml will make things just that bit nicer