Hi Anders, welcome to OCaml!
I’m practicing this language since 1999 and it’s excellent to read some fresh views from newcomers!
For the specific issue of Unicode it also depends on what you call “support” because Unicode is a very complex standard that as a lot of features. I personally use Camomile but there is hand of other libraries support part or all(?) of the Unicode features. Cf. opam search unicode
I did not know the document you found about ;; and ; and I am sad to say, it is needlessly confusing. First, they are two distinct tokens, so the compiler or the REPL read them differently, just as ++ and + in many other languages using a syntax similar to C. This should clarify the questions about whitespace significance. Just like removing a space in + + will change a sequence of two + into a single ++, removing a space in ; ; will change it into a single ;;. Second the ; is the sequence operator that we use in programs to say “compute this, then that” while the ;; is essentially an end of sequence signal for the REPL to tell the interpreter “please evaluate my statement.” For convenience, the compiler can also digest the ;; but it is not useful in compiled programs. I hope this helps to clarify the situation!
It is a detail but the lack of syntax highlighting could be caused by your terminal running the REPL. In my terminal (plain OS-X terminal) the user-input part triggering the error is underlined. On less capable terminals the system adds an extra line with carets as poor man’s underlining.
Just join us on https://discuss.ocaml.org, we can help you with your first steps as an OCaml-ler! :) Just as for any language, take some time to read other people’s code and look at how they organise their projects. GitHub features many repositories, e.g. https://github.com/michipili
We discussed your post on https://discuss.ocaml.org/t/ocaml-first-impressions/517/6